Virtualization - Jul 2016 - [PATCH 6/7] qemu: Implement virtio-pstore device

Hello,

This is v2 of the virtio-pstore work.  In this patchset I addressed
most of feedbacks from previous version.  Limiting disk size is not
implemented yet.

 * changes in v2)
  - update VIRTIO_ID_PSTORE to 22  (Cornelia, Stefan)
  - make buffer size configurable  (Cornelia)
  - support PSTORE_TYPE_CONSOLE  (Kees)
  - use separate virtqueues for read and write
  - support concurrent async write
  - manage pstore (file) id in device side
  - fix various mistakes in qemu device  (Stefan)

It started from the fact that dumping ftrace buffer at kernel
oops/panic takes too much time.  Although there's a way to reduce the
size of the original data, sometimes I want to have the information as
many as possible.  Maybe kexec/kdump can solve this problem but it
consumes some portion of guest memory so I'd like to avoid it.  And I
know the qemu + crashtool can dump and analyze the whole guest memory
including the ftrace buffer without wasting guest memory, but it adds
one more layer and has some limitation as an out-of-tree tool like not
being in sync with the kernel changes.

So I think it'd be great using the pstore interface to dump guest
kernel data on the host.  One can read the data on the host directly
or on the guest (at the next boot) using pstore filesystem as usual.
While this patchset only implements dumping kernel log buffer, it can
be extended to have ftrace buffer and probably some more..

The patch 0001-0003 are preparation for pstore to support virtio
device which requires async write.  The patch 0004 implements virtio
pstore driver.  It has two virt queue for (sync) read and (async)
write, pstore buffer and io request and response structure.  The
virtio_pstore_req struct is to give information about the current
pstore operation.  The result will be written to the virtio_pstore_res
struct.  For read operation it also uses virtio_pstore_fileinfo struct.

The patch 0005 adds support for PSTORE_TYPE_CONSOLE which was
requested by Kees.  The console data is appended to a single file for
now.

The patch 0006 and 0007 implement virtio-pstore legacy PCI device on
qemu-kvm and kvmtool respectively.  I referenced virtio-baloon and
virtio-rng implementations and I don't know whether kvmtool supports
modern virtio 1.0+ spec.  Other transports might be supported later.

For example, using virtio-pstore on qemu looks like below:

  $ qemu-system-x86_64 -enable-kvm -device virtio-pstore,directory=xxx

When guest kernel gets panic the log messages will be saved under the
xxx directory.

  $ ls xxx
  dmesg-1.enc.z  dmesg-2.enc.z

As you can see the pstore subsystem compresses the log data using zlib
(now supports lzo and lz4 too).  The data can be extracted with the
following command:

  $ cat xxx/dmesg-1.enc.z | \
  > python -c 'import sys, zlib;
print(zlib.decompress(sys.stdin.read()))'
  Oops#1 Part1
  <5>[    0.000000] Linux version 4.6.0kvm+ (namhyung at danjae) (gcc
version 5.3.0 (GCC) ) #145 SMP Mon Jul 18 10:22:45 KST 2016
  <6>[    0.000000] Command line: root=/dev/vda console=ttyS0
  <6>[    0.000000] x86/fpu: Legacy x87 FPU detected.
  <6>[    0.000000] x86/fpu: Using 'eager' FPU context switches.
  <6>[    0.000000] e820: BIOS-provided physical RAM map:
  <6>[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff]
usable
  <6>[    0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff]
reserved
  <6>[    0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff]
reserved
  <6>[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x0000000007fddfff]
usable
  <6>[    0.000000] BIOS-e820: [mem 0x0000000007fde000-0x0000000007ffffff]
reserved
  <6>[    0.000000] BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff]
reserved
  <6>[    0.000000] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff]
reserved
  <6>[    0.000000] NX (Execute Disable) protection: active
  <6>[    0.000000] SMBIOS 2.8 present.
  <7>[    0.000000] DMI: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
  ...

To enable PSTORE_TYPE_CONSOLE, add 'console=true' to virtio-pstore
device option.  Also 'bufsize' option can set different size for
pstore buffer (default is 16K).  Maybe we can add a config option to
control the compression later.

Currently the kvmtool doesn't support any options except the directory
the pstore saves the logs.


Namhyung Kim (7):
  pstore: Split pstore fragile flags
  pstore/ram: Set pstore flags dynamically
  pstore: Manage buffer position for async write
  virtio: Basic implementation of virtio pstore driver
  virtio-pstore: Support PSTORE_TYPE_CONSOLE
  qemu: Implement virtio-pstore device
  kvmtool: Implement virtio-pstore device

 drivers/acpi/apei/erst.c             |   2 +-
 drivers/firmware/efi/efi-pstore.c    |   4 +-
 drivers/virtio/Kconfig               |  10 +
 drivers/virtio/Makefile              |   1 +
 drivers/virtio/virtio_pstore.c       | 421 +++++++++++++++++++++
 fs/pstore/platform.c                 |  65 +++-
 fs/pstore/ram.c                      |   8 +
 include/linux/pstore.h               |   9 +-
 include/uapi/linux/Kbuild            |   1 +
 include/uapi/linux/virtio_ids.h      |   1 +
 include/uapi/linux/virtio_pstore.h   |  78 +++-
 11 files changed, 580 insertions(+), 20 deletions(-)
 create mode 100644 drivers/virtio/virtio_pstore.c
 create mode 100644 include/uapi/linux/virtio_pstore.h


Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Radim Kr?m?? <rkrcmar at redhat.com>
Cc: "Michael S. Tsirkin" <mst at redhat.com>
Cc: Anthony Liguori <aliguori at amazon.com>
Cc: Anton Vorontsov <anton at enomsg.org>
Cc: Colin Cross <ccross at android.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Steven Rostedt <rostedt at goodmis.org>
Cc: Ingo Molnar <mingo at kernel.org>
Cc: Minchan Kim <minchan at kernel.org>
Cc: Will Deacon <will.deacon at arm.com>
Cc: kvm at vger.kernel.org
Cc: qemu-devel at nongnu.org
Cc: virtualization at lists.linux-foundation.org

Thanks,
Namhyung


-- 
2.8.0

This patch adds new PSTORE_FLAGS for each pstore type so that they can
be enabled separately.  This is a preparation for ongoing virtio-pstore
work to support those types flexibly.

The PSTORE_FLAGS_FRAGILE is changed to PSTORE_FLAGS_DMESG to preserve the
original behavior.

Cc: Anton Vorontsov <anton at enomsg.org>
Cc: Colin Cross <ccross at android.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: "Rafael J. Wysocki" <rjw at rjwysocki.net>
Cc: Len Brown <lenb at kernel.org>
Cc: Matt Fleming <matt at codeblueprint.co.uk>
Cc: linux-acpi at vger.kernel.org
Cc: linux-efi at vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung at kernel.org>
---
 drivers/acpi/apei/erst.c          |  2 +-
 drivers/firmware/efi/efi-pstore.c |  2 +-
 fs/pstore/platform.c              | 17 ++++++++++-------
 fs/pstore/ram.c                   |  2 ++
 include/linux/pstore.h            |  7 ++++++-
 5 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
index f096ab3cb54d..ec4f507b524f 100644
--- a/drivers/acpi/apei/erst.c
+++ b/drivers/acpi/apei/erst.c
@@ -938,7 +938,7 @@ static int erst_clearer(enum pstore_type_id type, u64 id,
int count,
 static struct pstore_info erst_info = {
 	.owner		= THIS_MODULE,
 	.name		= "erst",
-	.flags		= PSTORE_FLAGS_FRAGILE,
+	.flags		= PSTORE_FLAGS_DMESG,
 	.open		= erst_open_pstore,
 	.close		= erst_close_pstore,
 	.read		= erst_reader,
diff --git a/drivers/firmware/efi/efi-pstore.c
b/drivers/firmware/efi/efi-pstore.c
index 30a24d09ea6c..4daa5acd9117 100644
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -362,7 +362,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64
id, int count,
 static struct pstore_info efi_pstore_info = {
 	.owner		= THIS_MODULE,
 	.name		= "efi",
-	.flags		= PSTORE_FLAGS_FRAGILE,
+	.flags		= PSTORE_FLAGS_DMESG,
 	.open		= efi_pstore_open,
 	.close		= efi_pstore_close,
 	.read		= efi_pstore_read,
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 16ecca5b72d8..76dd604a0f2c 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -659,13 +659,14 @@ int pstore_register(struct pstore_info *psi)
 	if (pstore_is_mounted())
 		pstore_get_records(0);
 
-	pstore_register_kmsg();
-
-	if ((psi->flags & PSTORE_FLAGS_FRAGILE) == 0) {
+	if (psi->flags & PSTORE_FLAGS_DMESG)
+		pstore_register_kmsg();
+	if (psi->flags & PSTORE_FLAGS_CONSOLE)
 		pstore_register_console();
+	if (psi->flags & PSTORE_FLAGS_FTRACE)
 		pstore_register_ftrace();
+	if (psi->flags & PSTORE_FLAGS_PMSG)
 		pstore_register_pmsg();
-	}
 
 	if (pstore_update_ms >= 0) {
 		pstore_timer.expires = jiffies +
@@ -689,12 +690,14 @@ EXPORT_SYMBOL_GPL(pstore_register);
 
 void pstore_unregister(struct pstore_info *psi)
 {
-	if ((psi->flags & PSTORE_FLAGS_FRAGILE) == 0) {
+	if (psi->flags & PSTORE_FLAGS_PMSG)
 		pstore_unregister_pmsg();
+	if (psi->flags & PSTORE_FLAGS_FTRACE)
 		pstore_unregister_ftrace();
+	if (psi->flags & PSTORE_FLAGS_CONSOLE)
 		pstore_unregister_console();
-	}
-	pstore_unregister_kmsg();
+	if (psi->flags & PSTORE_FLAGS_DMESG)
+		pstore_unregister_kmsg();
 
 	free_buf_for_compression();
 
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 47516a794011..ba19a74e95bc 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -624,6 +624,8 @@ static int ramoops_probe(struct platform_device *pdev)
 		goto fail_clear;
 	}
 
+	cxt->pstore.flags = PSTORE_FLAGS_ALL;
+
 	err = pstore_register(&cxt->pstore);
 	if (err) {
 		pr_err("registering with pstore failed\n");
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index 899e95e84400..069b96faf478 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -74,7 +74,12 @@ struct pstore_info {
 	void		*data;
 };
 
-#define	PSTORE_FLAGS_FRAGILE	1
+#define PSTORE_FLAGS_DMESG	(1 << 0)
+#define PSTORE_FLAGS_CONSOLE	(1 << 1)
+#define PSTORE_FLAGS_FTRACE	(1 << 2)
+#define PSTORE_FLAGS_PMSG	(1 << 3)
+
+#define PSTORE_FLAGS_ALL	((1 << 4) - 1)
 
 extern int pstore_register(struct pstore_info *);
 extern void pstore_unregister(struct pstore_info *);
-- 
2.8.0

The ramoops can be configured to enable each pstore type by setting
their size.  In that case, it'd be better not to register disabled types
in the first place.

Cc: Anton Vorontsov <anton at enomsg.org>
Cc: Colin Cross <ccross at android.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Tony Luck <tony.luck at intel.com>
Signed-off-by: Namhyung Kim <namhyung at kernel.org>
---
 fs/pstore/ram.c        | 8 +++++++-
 include/linux/pstore.h | 2 --
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index ba19a74e95bc..6c93268f7ced 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -624,7 +624,13 @@ static int ramoops_probe(struct platform_device *pdev)
 		goto fail_clear;
 	}
 
-	cxt->pstore.flags = PSTORE_FLAGS_ALL;
+	cxt->pstore.flags = PSTORE_FLAGS_DMESG;
+	if (cxt->console_size)
+		cxt->pstore.flags |= PSTORE_FLAGS_CONSOLE;
+	if (cxt->ftrace_size)
+		cxt->pstore.flags |= PSTORE_FLAGS_FTRACE;
+	if (cxt->pmsg_size)
+		cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
 
 	err = pstore_register(&cxt->pstore);
 	if (err) {
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index 069b96faf478..9790904de6d2 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -79,8 +79,6 @@ struct pstore_info {
 #define PSTORE_FLAGS_FTRACE	(1 << 2)
 #define PSTORE_FLAGS_PMSG	(1 << 3)
 
-#define PSTORE_FLAGS_ALL	((1 << 4) - 1)
-
 extern int pstore_register(struct pstore_info *);
 extern void pstore_unregister(struct pstore_info *);
 extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
-- 
2.8.0

Some pstore backend only supports async mode, so it's possible to do
some IO at the same time.  In this case we need to manage the single
psinfo->buf not to broken by concurrent IO.

For example PSTORE_TYPE_CONSOLE IO is serialized by psinfo->buf_lock but
later IO can be issued before finishing previous request.  In this case
it overwrites psinfo->buf so the previous result might be broken.

This patch adds psinfo->bufpos field to keep track of current position
in order to use psinfo->buf as a ring buffer.  However it's just a
simple, best-effort way of doing that, and provides no 100% guarantee.
It's only effective for small concurrent IO like PSTORE_TYPE_CONSOLE
IMHO.

The new PSTORE_FLAGS_ASYNC flag enables management of buffer position.
The pstore_prepare_buf() is called before accessing the psinfo->buf and
the pstore_update_buf() is called after accessing the buf.

The pstore_get_buf() is provided for psinfo->write callback to determine
the current position of available buffer.

Cc: Anton Vorontsov <anton at enomsg.org>
Cc: Colin Cross <ccross at android.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Matt Fleming <matt at codeblueprint.co.uk>
Cc: linux-efi at vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung at kernel.org>
---
 drivers/firmware/efi/efi-pstore.c |  2 +-
 fs/pstore/platform.c              | 48 +++++++++++++++++++++++++++++++--------
 include/linux/pstore.h            |  4 ++++
 3 files changed, 44 insertions(+), 10 deletions(-)

diff --git a/drivers/firmware/efi/efi-pstore.c
b/drivers/firmware/efi/efi-pstore.c
index 4daa5acd9117..ae0ffe259e07 100644
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -259,7 +259,7 @@ static int efi_pstore_write(enum pstore_type_id type,
 
 	efivar_entry_set_safe(efi_name, vendor, PSTORE_EFI_ATTRIBUTES,
 			      !pstore_cannot_block_path(reason),
-			      size, psi->buf);
+			      size, pstore_get_buf(psi));
 
 	if (reason == KMSG_DUMP_OOPS)
 		efivar_run_worker();
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 76dd604a0f2c..26e2808cf554 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -150,6 +150,27 @@ bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
 }
 EXPORT_SYMBOL_GPL(pstore_cannot_block_path);
 
+static void *pstore_prepare_buf(struct pstore_info *psi, size_t len)
+{
+	if (psi->bufpos + len > psi->bufsize ||
+	    (psi->flags & PSTORE_FLAGS_ASYNC) == 0)
+		psi->bufpos = 0;
+
+	return psi->buf + psi->bufpos;
+}
+
+static void pstore_update_buf(struct pstore_info *psi, size_t len)
+{
+	if (psi->flags & PSTORE_FLAGS_ASYNC)
+		psi->bufpos += len;
+}
+
+void *pstore_get_buf(struct pstore_info *psi)
+{
+	return psi->buf + psi->bufpos;
+}
+EXPORT_SYMBOL_GPL(pstore_get_buf);
+
 #ifdef CONFIG_PSTORE_ZLIB_COMPRESS
 /* Derived from logfs_compress() */
 static int compress_zlib(const void *in, void *out, size_t inlen, size_t
outlen)
@@ -455,18 +476,21 @@ static size_t copy_kmsg_to_buffer(int hsize, size_t len)
 {
 	size_t total_len;
 	size_t diff;
+	void *dst;
 
 	total_len = hsize + len;
+	dst = pstore_prepare_buf(psinfo, total_len);
 
 	if (total_len > psinfo->bufsize) {
 		diff = total_len - psinfo->bufsize + hsize;
-		memcpy(psinfo->buf, big_oops_buf, hsize);
-		memcpy(psinfo->buf + hsize, big_oops_buf + diff,
+		memcpy(dst, big_oops_buf, hsize);
+		memcpy(dst + hsize, big_oops_buf + diff,
 					psinfo->bufsize - hsize);
 		total_len = psinfo->bufsize;
 	} else
-		memcpy(psinfo->buf, big_oops_buf, total_len);
+		memcpy(dst, big_oops_buf, total_len);
 
+	pstore_update_buf(psinfo, total_len);
 	return total_len;
 }
 
@@ -500,7 +524,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 	}
 	oopscount++;
 	while (total < kmsg_bytes) {
-		char *dst;
+		char *dst, *buf;
 		unsigned long size;
 		int hsize;
 		int zipped_len = -1;
@@ -514,6 +538,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		} else {
 			dst = psinfo->buf;
 			size = psinfo->bufsize;
+			psinfo->bufpos = 0;
 		}
 
 		hsize = sprintf(dst, "%s#%d Part%u\n", why, oopscount, part);
@@ -524,8 +549,9 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 			break;
 
 		if (big_oops_buf && is_locked) {
-			zipped_len = pstore_compress(dst, psinfo->buf,
-						hsize + len, psinfo->bufsize);
+			buf = pstore_prepare_buf(psinfo, hsize + len);
+			zipped_len = pstore_compress(dst, buf, hsize + len,
+						psinfo->bufsize - psinfo->bufpos);
 
 			if (zipped_len > 0) {
 				compressed = true;
@@ -543,6 +569,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 			pstore_new_entry = 1;
 
 		total += total_len;
+		pstore_update_buf(psinfo, total_len);
 		part++;
 	}
 	if (is_locked)
@@ -573,6 +600,7 @@ static void pstore_console_write(struct console *con, const
char *s, unsigned c)
 
 	while (s < e) {
 		unsigned long flags;
+		void *dst;
 		u64 id;
 
 		if (c > psinfo->bufsize)
@@ -584,8 +612,10 @@ static void pstore_console_write(struct console *con, const
char *s, unsigned c)
 		} else {
 			spin_lock_irqsave(&psinfo->buf_lock, flags);
 		}
-		memcpy(psinfo->buf, s, c);
+		dst = pstore_prepare_buf(psinfo, c);
+		memcpy(dst, s, c);
 		psinfo->write(PSTORE_TYPE_CONSOLE, 0, &id, 0, 0, 0, c, psinfo);
+		pstore_update_buf(psinfo, c);
 		spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 		s += c;
 		c = e - s;
@@ -619,8 +649,8 @@ static int pstore_write_compat(enum pstore_type_id type,
 			       bool compressed, size_t size,
 			       struct pstore_info *psi)
 {
-	return psi->write_buf(type, reason, id, part, psinfo->buf, compressed,
-			     size, psi);
+	return psi->write_buf(type, reason, id, part, pstore_get_buf(psinfo),
+			      compressed, size, psi);
 }
 
 /*
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index 9790904de6d2..14f524177b1f 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -52,6 +52,7 @@ struct pstore_info {
 	spinlock_t	buf_lock;	/* serialize access to 'buf' */
 	char		*buf;
 	size_t		bufsize;
+	size_t		bufpos;
 	struct mutex	read_mutex;	/* serialize open/read/close */
 	int		flags;
 	int		(*open)(struct pstore_info *psi);
@@ -79,8 +80,11 @@ struct pstore_info {
 #define PSTORE_FLAGS_FTRACE	(1 << 2)
 #define PSTORE_FLAGS_PMSG	(1 << 3)
 
+#define PSTORE_FLAGS_ASYNC      (1 << 30)
+
 extern int pstore_register(struct pstore_info *);
 extern void pstore_unregister(struct pstore_info *);
 extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
+extern void *pstore_get_buf(struct pstore_info *);
 
 #endif /*_LINUX_PSTORE_H*/
-- 
2.8.0

The virtio pstore driver provides interface to the pstore subsystem so
that the guest kernel's log/dump message can be saved on the host
machine.  Users can access the log file directly on the host, or on the
guest at the next boot using pstore filesystem.  It currently deals with
kernel log (printk) buffer only, but we can extend it to have other
information (like ftrace dump) later.

It supports legacy PCI device using single order-2 page buffer.  It uses
two virtqueues - one for (sync) read and another for (async) write.
Since it cannot wait for write finished, it supports up to 128
concurrent IO.  The buffer size is configurable now.

Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Radim Kr?m?? <rkrcmar at redhat.com>
Cc: "Michael S. Tsirkin" <mst at redhat.com>
Cc: Anthony Liguori <aliguori at amazon.com>
Cc: Anton Vorontsov <anton at enomsg.org>
Cc: Colin Cross <ccross at android.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Steven Rostedt <rostedt at goodmis.org>
Cc: Ingo Molnar <mingo at kernel.org>
Cc: Minchan Kim <minchan at kernel.org>
Cc: kvm at vger.kernel.org
Cc: qemu-devel at nongnu.org
Cc: virtualization at lists.linux-foundation.org
Signed-off-by: Namhyung Kim <namhyung at kernel.org>
---
 drivers/virtio/Kconfig             |  10 +
 drivers/virtio/Makefile            |   1 +
 drivers/virtio/virtio_pstore.c     | 414 +++++++++++++++++++++++++++++++++++++
 include/uapi/linux/Kbuild          |   1 +
 include/uapi/linux/virtio_ids.h    |   1 +
 include/uapi/linux/virtio_pstore.h |  74 +++++++
 6 files changed, 501 insertions(+)
 create mode 100644 drivers/virtio/virtio_pstore.c
 create mode 100644 include/uapi/linux/virtio_pstore.h

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 77590320d44c..8f0e6c796c12 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -58,6 +58,16 @@ config VIRTIO_INPUT
 
 	 If unsure, say M.
 
+config VIRTIO_PSTORE
+	tristate "Virtio pstore driver"
+	depends on VIRTIO
+	depends on PSTORE
+	---help---
+	 This driver supports virtio pstore devices to save/restore
+	 panic and oops messages on the host.
+
+	 If unsure, say M.
+
  config VIRTIO_MMIO
 	tristate "Platform bus driver for memory mapped virtio devices"
 	depends on HAS_IOMEM && HAS_DMA
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 41e30e3dc842..bee68cb26d48 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -5,3 +5,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
 virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
+obj-$(CONFIG_VIRTIO_PSTORE) += virtio_pstore.o
diff --git a/drivers/virtio/virtio_pstore.c b/drivers/virtio/virtio_pstore.c
new file mode 100644
index 000000000000..4ee1c186f582
--- /dev/null
+++ b/drivers/virtio/virtio_pstore.c
@@ -0,0 +1,414 @@
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pstore.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <uapi/linux/virtio_ids.h>
+#include <uapi/linux/virtio_pstore.h>
+
+#define VIRT_PSTORE_ORDER    2
+#define VIRT_PSTORE_BUFSIZE  (4096 << VIRT_PSTORE_ORDER)
+#define VIRT_PSTORE_NR_REQ   128
+
+struct virtio_pstore {
+	struct virtio_device	*vdev;
+	struct virtqueue	*vq[2];
+	struct pstore_info	 pstore;
+	struct virtio_pstore_req req[VIRT_PSTORE_NR_REQ];
+	struct virtio_pstore_res res[VIRT_PSTORE_NR_REQ];
+	unsigned int		 req_id;
+
+	/* Waiting for host to ack */
+	wait_queue_head_t	acked;
+	int			failed;
+};
+
+#define TYPE_TABLE_ENTRY(_entry)				\
+	{ PSTORE_TYPE_##_entry, VIRTIO_PSTORE_TYPE_##_entry }
+
+struct type_table {
+	int pstore;
+	u16 virtio;
+} type_table[] = {
+	TYPE_TABLE_ENTRY(DMESG),
+};
+
+#undef TYPE_TABLE_ENTRY
+
+
+static u16 to_virtio_type(struct virtio_pstore *vps, enum pstore_type_id type)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(type_table); i++) {
+		if (type == type_table[i].pstore)
+			return cpu_to_virtio16(vps->vdev, type_table[i].virtio);
+	}
+
+	return cpu_to_virtio16(vps->vdev, VIRTIO_PSTORE_TYPE_UNKNOWN);
+}
+
+static enum pstore_type_id from_virtio_type(struct virtio_pstore *vps, u16
type)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(type_table); i++) {
+		if (virtio16_to_cpu(vps->vdev, type) == type_table[i].virtio)
+			return type_table[i].pstore;
+	}
+
+	return PSTORE_TYPE_UNKNOWN;
+}
+
+static void virtpstore_ack(struct virtqueue *vq)
+{
+	struct virtio_pstore *vps = vq->vdev->priv;
+
+	wake_up(&vps->acked);
+}
+
+static void virtpstore_check(struct virtqueue *vq)
+{
+	struct virtio_pstore *vps = vq->vdev->priv;
+	struct virtio_pstore_res *res;
+	unsigned int len;
+
+	res = virtqueue_get_buf(vq, &len);
+	if (res == NULL)
+		return;
+
+	if (virtio32_to_cpu(vq->vdev, res->ret) < 0)
+		vps->failed = 1;
+}
+
+static void virt_pstore_get_reqs(struct virtio_pstore *vps,
+				 struct virtio_pstore_req **preq,
+				 struct virtio_pstore_res **pres)
+{
+	unsigned int idx = vps->req_id++ % VIRT_PSTORE_NR_REQ;
+
+	*preq = &vps->req[idx];
+	*pres = &vps->res[idx];
+
+	memset(*preq, 0, sizeof(**preq));
+	memset(*pres, 0, sizeof(**pres));
+}
+
+static int virt_pstore_open(struct pstore_info *psi)
+{
+	struct virtio_pstore *vps = psi->data;
+	struct virtio_pstore_req *req;
+	struct virtio_pstore_res *res;
+	struct scatterlist sgo[1], sgi[1];
+	struct scatterlist *sgs[2] = { sgo, sgi };
+	unsigned int len;
+
+	virt_pstore_get_reqs(vps, &req, &res);
+
+	req->cmd = cpu_to_virtio16(vps->vdev, VIRTIO_PSTORE_CMD_OPEN);
+
+	sg_init_one(sgo, req, sizeof(*req));
+	sg_init_one(sgi, res, sizeof(*res));
+	virtqueue_add_sgs(vps->vq[0], sgs, 1, 1, vps, GFP_KERNEL);
+	virtqueue_kick(vps->vq[0]);
+
+	wait_event(vps->acked, virtqueue_get_buf(vps->vq[0], &len));
+	return virtio32_to_cpu(vps->vdev, res->ret);
+}
+
+static int virt_pstore_close(struct pstore_info *psi)
+{
+	struct virtio_pstore *vps = psi->data;
+	struct virtio_pstore_req *req = &vps->req[vps->req_id];
+	struct virtio_pstore_res *res = &vps->res[vps->req_id];
+	struct scatterlist sgo[1], sgi[1];
+	struct scatterlist *sgs[2] = { sgo, sgi };
+	unsigned int len;
+
+	virt_pstore_get_reqs(vps, &req, &res);
+
+	req->cmd = cpu_to_virtio16(vps->vdev, VIRTIO_PSTORE_CMD_CLOSE);
+
+	sg_init_one(sgo, req, sizeof(*req));
+	sg_init_one(sgi, res, sizeof(*res));
+	virtqueue_add_sgs(vps->vq[0], sgs, 1, 1, vps, GFP_KERNEL);
+	virtqueue_kick(vps->vq[0]);
+
+	wait_event(vps->acked, virtqueue_get_buf(vps->vq[0], &len));
+	return virtio32_to_cpu(vps->vdev, res->ret);
+}
+
+static ssize_t virt_pstore_read(u64 *id, enum pstore_type_id *type,
+				int *count, struct timespec *time,
+				char **buf, bool *compressed,
+				ssize_t *ecc_notice_size,
+				struct pstore_info *psi)
+{
+	struct virtio_pstore *vps = psi->data;
+	struct virtio_pstore_req *req;
+	struct virtio_pstore_res *res;
+	struct virtio_pstore_fileinfo info;
+	struct scatterlist sgo[1], sgi[3];
+	struct scatterlist *sgs[2] = { sgo, sgi };
+	unsigned int len;
+	unsigned int flags;
+	int ret;
+	void *bf;
+
+	virt_pstore_get_reqs(vps, &req, &res);
+
+	req->cmd = cpu_to_virtio16(vps->vdev, VIRTIO_PSTORE_CMD_READ);
+
+	sg_init_one(sgo, req, sizeof(*req));
+	sg_init_table(sgi, 3);
+	sg_set_buf(&sgi[0], res, sizeof(*res));
+	sg_set_buf(&sgi[1], &info, sizeof(info));
+	sg_set_buf(&sgi[2], psi->buf, psi->bufsize);
+	virtqueue_add_sgs(vps->vq[0], sgs, 1, 1, vps, GFP_KERNEL);
+	virtqueue_kick(vps->vq[0]);
+
+	wait_event(vps->acked, virtqueue_get_buf(vps->vq[0], &len));
+	if (len < sizeof(*res) + sizeof(info))
+		return -1;
+
+	ret = virtio32_to_cpu(vps->vdev, res->ret);
+	if (ret < 0)
+		return ret;
+
+	len = virtio32_to_cpu(vps->vdev, info.len);
+
+	bf = kmalloc(len, GFP_KERNEL);
+	if (bf == NULL)
+		return -ENOMEM;
+
+	*id    = virtio64_to_cpu(vps->vdev, info.id);
+	*type  = from_virtio_type(vps, info.type);
+	*count = virtio32_to_cpu(vps->vdev, info.count);
+
+	flags = virtio32_to_cpu(vps->vdev, info.flags);
+	*compressed = flags & VIRTIO_PSTORE_FL_COMPRESSED;
+
+	time->tv_sec  = virtio64_to_cpu(vps->vdev, info.time_sec);
+	time->tv_nsec = virtio32_to_cpu(vps->vdev, info.time_nsec);
+
+	memcpy(bf, psi->buf, len);
+	*buf = bf;
+
+	return len;
+}
+
+static int notrace virt_pstore_write(enum pstore_type_id type,
+				     enum kmsg_dump_reason reason,
+				     u64 *id, unsigned int part, int count,
+				     bool compressed, size_t size,
+				     struct pstore_info *psi)
+{
+	struct virtio_pstore *vps = psi->data;
+	struct virtio_pstore_req *req;
+	struct virtio_pstore_res *res;
+	struct scatterlist sgo[2], sgi[1];
+	struct scatterlist *sgs[2] = { sgo, sgi };
+	unsigned int flags = compressed ? VIRTIO_PSTORE_FL_COMPRESSED : 0;
+
+	*id = vps->req_id;
+	virt_pstore_get_reqs(vps, &req, &res);
+
+	req->cmd   = cpu_to_virtio16(vps->vdev, VIRTIO_PSTORE_CMD_WRITE);
+	req->type  = to_virtio_type(vps, type);
+	req->flags = cpu_to_virtio32(vps->vdev, flags);
+
+	sg_init_table(sgo, 2);
+	sg_set_buf(&sgo[0], req, sizeof(*req));
+	sg_set_buf(&sgo[1], pstore_get_buf(psi), size);
+	sg_init_one(sgi, res, sizeof(*res));
+	virtqueue_add_sgs(vps->vq[1], sgs, 1, 1, vps, GFP_ATOMIC);
+	virtqueue_kick(vps->vq[1]);
+
+	return 0;
+}
+
+static int virt_pstore_erase(enum pstore_type_id type, u64 id, int count,
+			     struct timespec time, struct pstore_info *psi)
+{
+	struct virtio_pstore *vps = psi->data;
+	struct virtio_pstore_req *req;
+	struct virtio_pstore_res *res;
+	struct scatterlist sgo[1], sgi[1];
+	struct scatterlist *sgs[2] = { sgo, sgi };
+	unsigned int len;
+
+	virt_pstore_get_reqs(vps, &req, &res);
+
+	req->cmd   = cpu_to_virtio16(vps->vdev, VIRTIO_PSTORE_CMD_ERASE);
+	req->type  = to_virtio_type(vps, type);
+	req->id	   = cpu_to_virtio64(vps->vdev, id);
+	req->count = cpu_to_virtio32(vps->vdev, count);
+
+	sg_init_one(sgo, req, sizeof(*req));
+	sg_init_one(sgi, res, sizeof(*res));
+	virtqueue_add_sgs(vps->vq[0], sgs, 1, 1, vps, GFP_KERNEL);
+	virtqueue_kick(vps->vq[0]);
+
+	wait_event(vps->acked, virtqueue_get_buf(vps->vq[0], &len));
+	return virtio32_to_cpu(vps->vdev, res->ret);
+}
+
+static int virt_pstore_init(struct virtio_pstore *vps)
+{
+	struct pstore_info *psinfo = &vps->pstore;
+	int err;
+
+	if (!psinfo->bufsize)
+		psinfo->bufsize = VIRT_PSTORE_BUFSIZE;
+
+	psinfo->buf = alloc_pages_exact(psinfo->bufsize, GFP_KERNEL);
+	if (!psinfo->buf) {
+		pr_err("cannot allocate pstore buffer\n");
+		return -ENOMEM;
+	}
+
+	psinfo->owner = THIS_MODULE;
+	psinfo->name  = "virtio";
+	psinfo->open  = virt_pstore_open;
+	psinfo->close = virt_pstore_close;
+	psinfo->read  = virt_pstore_read;
+	psinfo->erase = virt_pstore_erase;
+	psinfo->write = virt_pstore_write;
+	psinfo->flags = PSTORE_FLAGS_DMESG;
+
+	psinfo->data  = vps;
+	spin_lock_init(&psinfo->buf_lock);
+
+	err = pstore_register(psinfo);
+	if (err)
+		kfree(psinfo->buf);
+
+	return err;
+}
+
+static int virt_pstore_exit(struct virtio_pstore *vps)
+{
+	struct pstore_info *psinfo = &vps->pstore;
+
+	pstore_unregister(psinfo);
+
+	free_pages_exact(psinfo->buf, psinfo->bufsize);
+	psinfo->buf = NULL;
+	psinfo->bufsize = 0;
+
+	return 0;
+}
+
+static int virtpstore_init_vqs(struct virtio_pstore *vps)
+{
+	vq_callback_t *callbacks[] = { virtpstore_ack, virtpstore_check };
+	const char *names[] = { "pstore_read", "pstore_write" };
+
+	return vps->vdev->config->find_vqs(vps->vdev, 2, vps->vq,
+					   callbacks, names);
+}
+
+static void virtpstore_init_config(struct virtio_pstore *vps)
+{
+	u32 bufsize;
+
+	virtio_cread(vps->vdev, struct virtio_pstore_config, bufsize,
&bufsize);
+
+	vps->pstore.bufsize = PAGE_ALIGN(bufsize);
+}
+
+static void virtpstore_confirm_config(struct virtio_pstore *vps)
+{
+	u32 bufsize = vps->pstore.bufsize;
+
+	virtio_cwrite(vps->vdev, struct virtio_pstore_config, bufsize,
+		     &bufsize);
+}
+
+static int virtpstore_probe(struct virtio_device *vdev)
+{
+	struct virtio_pstore *vps;
+	int err;
+
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "driver init: config access
disabled\n");
+		return -EINVAL;
+	}
+
+	vdev->priv = vps = kzalloc(sizeof(*vps), GFP_KERNEL);
+	if (!vps) {
+		err = -ENOMEM;
+		goto out;
+	}
+	vps->vdev = vdev;
+
+	err = virtpstore_init_vqs(vps);
+	if (err < 0)
+		goto out_free;
+
+	virtpstore_init_config(vps);
+
+	err = virt_pstore_init(vps);
+	if (err)
+		goto out_del_vq;
+
+	virtpstore_confirm_config(vps);
+
+	init_waitqueue_head(&vps->acked);
+
+	virtio_device_ready(vdev);
+
+	dev_info(&vdev->dev, "driver init: ok (bufsize = %luK, flags =
%x)\n",
+		 vps->pstore.bufsize >> 10, vps->pstore.flags);
+
+	return 0;
+
+out_del_vq:
+	vdev->config->del_vqs(vdev);
+out_free:
+	kfree(vps);
+out:
+	dev_err(&vdev->dev, "driver init: failed with %d\n", err);
+	return err;
+}
+
+static void virtpstore_remove(struct virtio_device *vdev)
+{
+	struct virtio_pstore *vps = vdev->priv;
+
+	virt_pstore_exit(vps);
+
+	/* Now we reset the device so we can clean up the queues. */
+	vdev->config->reset(vdev);
+
+	vdev->config->del_vqs(vdev);
+
+	kfree(vps);
+}
+
+static unsigned int features[] = {
+};
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_PSTORE, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static struct virtio_driver virtio_pstore_driver = {
+	.driver.name         = KBUILD_MODNAME,
+	.driver.owner        = THIS_MODULE,
+	.feature_table       = features,
+	.feature_table_size  = ARRAY_SIZE(features),
+	.id_table            = id_table,
+	.probe               = virtpstore_probe,
+	.remove              = virtpstore_remove,
+};
+
+module_virtio_driver(virtio_pstore_driver);
+MODULE_DEVICE_TABLE(virtio, id_table);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Namhyung Kim <namhyung at kernel.org>");
+MODULE_DESCRIPTION("Virtio pstore driver");
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index ec10cfef166a..c3a7d56599c5 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -449,6 +449,7 @@ header-y += virtio_ids.h
 header-y += virtio_input.h
 header-y += virtio_net.h
 header-y += virtio_pci.h
+header-y += virtio_pstore.h
 header-y += virtio_ring.h
 header-y += virtio_rng.h
 header-y += virtio_scsi.h
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 77925f587b15..c72a9ab588c0 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -41,5 +41,6 @@
 #define VIRTIO_ID_CAIF	       12 /* Virtio caif */
 #define VIRTIO_ID_GPU          16 /* virtio GPU */
 #define VIRTIO_ID_INPUT        18 /* virtio input */
+#define VIRTIO_ID_PSTORE       22 /* virtio pstore */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
diff --git a/include/uapi/linux/virtio_pstore.h
b/include/uapi/linux/virtio_pstore.h
new file mode 100644
index 000000000000..f4b0d204d8ae
--- /dev/null
+++ b/include/uapi/linux/virtio_pstore.h
@@ -0,0 +1,74 @@
+#ifndef _LINUX_VIRTIO_PSTORE_H
+#define _LINUX_VIRTIO_PSTORE_H
+/* This header is BSD licensed so anyone can use the definitions to implement
+ * compatible drivers/servers.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of IBM nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE. */
+#include <linux/types.h>
+#include <linux/virtio_types.h>
+
+#define VIRTIO_PSTORE_CMD_NULL   0
+#define VIRTIO_PSTORE_CMD_OPEN   1
+#define VIRTIO_PSTORE_CMD_READ   2
+#define VIRTIO_PSTORE_CMD_WRITE  3
+#define VIRTIO_PSTORE_CMD_ERASE  4
+#define VIRTIO_PSTORE_CMD_CLOSE  5
+
+#define VIRTIO_PSTORE_TYPE_UNKNOWN  0
+#define VIRTIO_PSTORE_TYPE_DMESG    1
+
+#define VIRTIO_PSTORE_FL_COMPRESSED  1
+
+struct virtio_pstore_req {
+	__virtio16		cmd;
+	__virtio16		type;
+	__virtio32		flags;
+	__virtio64		id;
+	__virtio32		count;
+	__virtio32		reserved;
+};
+
+struct virtio_pstore_res {
+	__virtio16		cmd;
+	__virtio16		type;
+	__virtio32		ret;
+};
+
+struct virtio_pstore_fileinfo {
+	__virtio64		id;
+	__virtio32		count;
+	__virtio16		type;
+	__virtio16		unused;
+	__virtio32		flags;
+	__virtio32		len;
+	__virtio64		time_sec;
+	__virtio32		time_nsec;
+	__virtio32		reserved;
+};
+
+struct virtio_pstore_config {
+	__virtio32		bufsize;
+};
+
+#endif /* _LINUX_VIRTIO_PSTORE_H */
-- 
2.8.0

With help of buffer management functions, it now supports CONSOLE type
pstore write.  The config space has flags field which defines the
VIRTIO_PSTORE_CONFIG_FL_CONSOLE.  When it's set, the virtio-pstore
driver also sets PSTORE_FLAGS_ASYNC so that the buffer management is
enabled.

Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Radim Kr?m?? <rkrcmar at redhat.com>
Cc: "Michael S. Tsirkin" <mst at redhat.com>
Cc: Anthony Liguori <aliguori at amazon.com>
Cc: Anton Vorontsov <anton at enomsg.org>
Cc: Colin Cross <ccross at android.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Steven Rostedt <rostedt at goodmis.org>
Cc: Ingo Molnar <mingo at kernel.org>
Cc: Minchan Kim <minchan at kernel.org>
Cc: kvm at vger.kernel.org
Cc: qemu-devel at nongnu.org
Cc: virtualization at lists.linux-foundation.org
Signed-off-by: Namhyung Kim <namhyung at kernel.org>
---
 drivers/virtio/virtio_pstore.c     | 9 ++++++++-
 include/uapi/linux/virtio_pstore.h | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_pstore.c b/drivers/virtio/virtio_pstore.c
index 4ee1c186f582..458c4d3ccbb1 100644
--- a/drivers/virtio/virtio_pstore.c
+++ b/drivers/virtio/virtio_pstore.c
@@ -33,6 +33,7 @@ struct type_table {
 	u16 virtio;
 } type_table[] = {
 	TYPE_TABLE_ENTRY(DMESG),
+	TYPE_TABLE_ENTRY(CONSOLE),
 };
 
 #undef TYPE_TABLE_ENTRY
@@ -276,7 +277,8 @@ static int virt_pstore_init(struct virtio_pstore *vps)
 	psinfo->read  = virt_pstore_read;
 	psinfo->erase = virt_pstore_erase;
 	psinfo->write = virt_pstore_write;
-	psinfo->flags = PSTORE_FLAGS_DMESG;
+	/* preserve flags from config */
+	psinfo->flags |= PSTORE_FLAGS_DMESG;
 
 	psinfo->data  = vps;
 	spin_lock_init(&psinfo->buf_lock);
@@ -313,10 +315,15 @@ static int virtpstore_init_vqs(struct virtio_pstore *vps)
 static void virtpstore_init_config(struct virtio_pstore *vps)
 {
 	u32 bufsize;
+	u32 flags;
 
 	virtio_cread(vps->vdev, struct virtio_pstore_config, bufsize,
&bufsize);
+	virtio_cread(vps->vdev, struct virtio_pstore_config, flags, &flags);
 
 	vps->pstore.bufsize = PAGE_ALIGN(bufsize);
+
+	if (flags & VIRTIO_PSTORE_CONFIG_FL_CONSOLE)
+		vps->pstore.flags |= PSTORE_FLAGS_CONSOLE | PSTORE_FLAGS_ASYNC;
 }
 
 static void virtpstore_confirm_config(struct virtio_pstore *vps)
diff --git a/include/uapi/linux/virtio_pstore.h
b/include/uapi/linux/virtio_pstore.h
index f4b0d204d8ae..56d0b1554231 100644
--- a/include/uapi/linux/virtio_pstore.h
+++ b/include/uapi/linux/virtio_pstore.h
@@ -37,9 +37,12 @@
 
 #define VIRTIO_PSTORE_TYPE_UNKNOWN  0
 #define VIRTIO_PSTORE_TYPE_DMESG    1
+#define VIRTIO_PSTORE_TYPE_CONSOLE  2
 
 #define VIRTIO_PSTORE_FL_COMPRESSED  1
 
+#define VIRTIO_PSTORE_CONFIG_FL_CONSOLE  (1 << 0)
+
 struct virtio_pstore_req {
 	__virtio16		cmd;
 	__virtio16		type;
@@ -69,6 +72,7 @@ struct virtio_pstore_fileinfo {
 
 struct virtio_pstore_config {
 	__virtio32		bufsize;
+	__virtio32		flags;
 };
 
 #endif /* _LINUX_VIRTIO_PSTORE_H */
-- 
2.8.0

Add virtio pstore device to allow kernel log files saved on the host.
It will save the log files on the directory given by pstore device
option.

  $ qemu-system-x86_64 -device virtio-pstore,directory=dir-xx ...

  (guest) # echo c > /proc/sysrq-trigger

  $ ls dir-xx
  dmesg-1.enc.z  dmesg-2.enc.z

The log files are usually compressed using zlib.  Users can see the log
messages directly on the host or on the guest (using pstore filesystem).

The 'directory' property is required for virtio-pstore device to work.
It also adds 'bufsize' and 'console' (boolean) properties.

Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Radim Kr?m?? <rkrcmar at redhat.com>
Cc: "Michael S. Tsirkin" <mst at redhat.com>
Cc: Anthony Liguori <aliguori at amazon.com>
Cc: Anton Vorontsov <anton at enomsg.org>
Cc: Colin Cross <ccross at android.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Steven Rostedt <rostedt at goodmis.org>
Cc: Ingo Molnar <mingo at kernel.org>
Cc: Minchan Kim <minchan at kernel.org>
Cc: kvm at vger.kernel.org
Cc: qemu-devel at nongnu.org
Cc: virtualization at lists.linux-foundation.org
Signed-off-by: Namhyung Kim <namhyung at kernel.org>
---
 hw/virtio/Makefile.objs                        |   2 +-
 hw/virtio/virtio-pci.c                         |  54 +++
 hw/virtio/virtio-pci.h                         |  14 +
 hw/virtio/virtio-pstore.c                      | 477 +++++++++++++++++++++++++
 include/hw/pci/pci.h                           |   1 +
 include/hw/virtio/virtio-pstore.h              |  34 ++
 include/standard-headers/linux/virtio_ids.h    |   1 +
 include/standard-headers/linux/virtio_pstore.h |  80 +++++
 qdev-monitor.c                                 |   1 +
 9 files changed, 663 insertions(+), 1 deletion(-)
 create mode 100644 hw/virtio/virtio-pstore.c
 create mode 100644 include/hw/virtio/virtio-pstore.h
 create mode 100644 include/standard-headers/linux/virtio_pstore.h

diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
index 3e2b175..aae7082 100644
--- a/hw/virtio/Makefile.objs
+++ b/hw/virtio/Makefile.objs
@@ -4,4 +4,4 @@ common-obj-y += virtio-bus.o
 common-obj-y += virtio-mmio.o
 
 obj-y += virtio.o virtio-balloon.o 
-obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
+obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o virtio-pstore.o
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index f0677b7..d99a405 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -2414,6 +2414,59 @@ static const TypeInfo virtio_host_pci_info = {
 };
 #endif
 
+/* virtio-pstore-pci */
+
+static void virtio_pstore_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
+{
+    VirtIOPstorePCI *vps = VIRTIO_PSTORE_PCI(vpci_dev);
+    DeviceState *vdev = DEVICE(&vps->vdev);
+    Error *err = NULL;
+
+    qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
+    object_property_set_bool(OBJECT(vdev), true, "realized",
&err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
+}
+
+static void virtio_pstore_pci_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass);
+    PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass);
+
+    k->realize = virtio_pstore_pci_realize;
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+
+    pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
+    pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_PSTORE;
+    pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
+    pcidev_k->class_id = PCI_CLASS_OTHERS;
+}
+
+static void virtio_pstore_pci_instance_init(Object *obj)
+{
+    VirtIOPstorePCI *dev = VIRTIO_PSTORE_PCI(obj);
+
+    virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev),
+                                TYPE_VIRTIO_PSTORE);
+    object_property_add_alias(obj, "directory",
OBJECT(&dev->vdev),
+                              "directory", &error_abort);
+    object_property_add_alias(obj, "bufsize",
OBJECT(&dev->vdev),
+                              "bufsize", &error_abort);
+    object_property_add_alias(obj, "console",
OBJECT(&dev->vdev),
+                              "console", &error_abort);
+}
+
+static const TypeInfo virtio_pstore_pci_info = {
+    .name          = TYPE_VIRTIO_PSTORE_PCI,
+    .parent        = TYPE_VIRTIO_PCI,
+    .instance_size = sizeof(VirtIOPstorePCI),
+    .instance_init = virtio_pstore_pci_instance_init,
+    .class_init    = virtio_pstore_pci_class_init,
+};
+
 /* virtio-pci-bus */
 
 static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
@@ -2483,6 +2536,7 @@ static void virtio_pci_register_types(void)
 #ifdef CONFIG_VHOST_SCSI
     type_register_static(&vhost_scsi_pci_info);
 #endif
+    type_register_static(&virtio_pstore_pci_info);
 }
 
 type_init(virtio_pci_register_types)
diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
index e4548c2..b4c039f 100644
--- a/hw/virtio/virtio-pci.h
+++ b/hw/virtio/virtio-pci.h
@@ -31,6 +31,7 @@
 #ifdef CONFIG_VHOST_SCSI
 #include "hw/virtio/vhost-scsi.h"
 #endif
+#include "hw/virtio/virtio-pstore.h"
 
 typedef struct VirtIOPCIProxy VirtIOPCIProxy;
 typedef struct VirtIOBlkPCI VirtIOBlkPCI;
@@ -44,6 +45,7 @@ typedef struct VirtIOInputPCI VirtIOInputPCI;
 typedef struct VirtIOInputHIDPCI VirtIOInputHIDPCI;
 typedef struct VirtIOInputHostPCI VirtIOInputHostPCI;
 typedef struct VirtIOGPUPCI VirtIOGPUPCI;
+typedef struct VirtIOPstorePCI VirtIOPstorePCI;
 
 /* virtio-pci-bus */
 
@@ -311,6 +313,18 @@ struct VirtIOGPUPCI {
     VirtIOGPU vdev;
 };
 
+/*
+ * virtio-pstore-pci: This extends VirtioPCIProxy.
+ */
+#define TYPE_VIRTIO_PSTORE_PCI "virtio-pstore-pci"
+#define VIRTIO_PSTORE_PCI(obj) \
+        OBJECT_CHECK(VirtIOPstorePCI, (obj), TYPE_VIRTIO_PSTORE_PCI)
+
+struct VirtIOPstorePCI {
+    VirtIOPCIProxy parent_obj;
+    VirtIOPstore vdev;
+};
+
 /* Virtio ABI version, if we increment this, we break the guest driver. */
 #define VIRTIO_PCI_ABI_VERSION          0
 
diff --git a/hw/virtio/virtio-pstore.c b/hw/virtio/virtio-pstore.c
new file mode 100644
index 0000000..2ca7786
--- /dev/null
+++ b/hw/virtio/virtio-pstore.c
@@ -0,0 +1,477 @@
+/*
+ * Virtio Pstore Device
+ *
+ * Copyright (C) 2016  LG Electronics
+ *
+ * Authors:
+ *  Namhyung Kim  <namhyung at gmail.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include <stdio.h>
+
+#include "qemu/osdep.h"
+#include "qemu/iov.h"
+#include "qemu-common.h"
+#include "qemu/cutils.h"
+#include "qemu/error-report.h"
+#include "sysemu/kvm.h"
+#include "qapi/visitor.h"
+#include "qapi-event.h"
+#include "trace.h"
+
+#include "hw/virtio/virtio.h"
+#include "hw/virtio/virtio-bus.h"
+#include "hw/virtio/virtio-access.h"
+#include "hw/virtio/virtio-pstore.h"
+
+
+static void virtio_pstore_to_filename(VirtIOPstore *s, char *buf, size_t sz,
+                                      struct virtio_pstore_req *req)
+{
+    const char *basename;
+    unsigned long long id = 0;
+    unsigned int flags = le32_to_cpu(req->flags);
+
+    switch (le16_to_cpu(req->type)) {
+    case VIRTIO_PSTORE_TYPE_DMESG:
+        basename = "dmesg";
+        id = s->id++;
+        break;
+    case VIRTIO_PSTORE_TYPE_CONSOLE:
+        basename = "console";
+        if (s->console_id) {
+            id = s->console_id;
+        } else {
+            id = s->console_id = s->id++;
+        }
+        break;
+    default:
+        basename = "unknown";
+        break;
+    }
+
+    snprintf(buf, sz, "%s/%s-%llu%s", s->directory, basename, id,
+             flags & VIRTIO_PSTORE_FL_COMPRESSED ? ".enc.z" :
"");
+}
+
+static void virtio_pstore_from_filename(VirtIOPstore *s, char *name,
+                                        char *buf, size_t sz,
+                                        struct virtio_pstore_fileinfo *info)
+{
+    snprintf(buf, sz, "%s/%s", s->directory, name);
+
+    if (g_str_has_prefix(name, "dmesg-")) {
+        info->type = VIRTIO_PSTORE_TYPE_DMESG;
+        name += strlen("dmesg-");
+    } else if (g_str_has_prefix(name, "console-")) {
+        info->type = VIRTIO_PSTORE_TYPE_CONSOLE;
+        name += strlen("console-");
+    } else if (g_str_has_prefix(name, "unknown-")) {
+        info->type = VIRTIO_PSTORE_TYPE_UNKNOWN;
+        name += strlen("unknown-");
+    }
+
+    qemu_strtoull(name, NULL, 0, &info->id);
+
+    info->flags = 0;
+    if (g_str_has_suffix(name, ".enc.z")) {
+        info->flags |= VIRTIO_PSTORE_FL_COMPRESSED;
+    }
+}
+
+static ssize_t virtio_pstore_do_open(VirtIOPstore *s)
+{
+    s->dirp = opendir(s->directory);
+    if (s->dirp == NULL) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static ssize_t virtio_pstore_do_read(VirtIOPstore *s, struct iovec *in_sg,
+                                     unsigned int in_num,
+                                     struct virtio_pstore_res *res)
+{
+    char path[PATH_MAX];
+    int fd;
+    ssize_t len;
+    struct stat stbuf;
+    struct dirent *dent;
+    int sg_num = in_num;
+    struct iovec sg[sg_num];
+    struct virtio_pstore_fileinfo info;
+    size_t offset = sizeof(*res) + sizeof(info);
+
+    if (s->dirp == NULL) {
+        return -1;
+    }
+
+    dent = readdir(s->dirp);
+    while (dent) {
+        if (dent->d_name[0] != '.') {
+            break;
+        }
+        dent = readdir(s->dirp);
+    }
+
+    if (dent == NULL) {
+        return 0;
+    }
+
+    /* skip res and fileinfo */
+    sg_num = iov_copy(sg, sg_num, in_sg, in_num, offset,
+                      iov_size(in_sg, in_num) - offset);
+
+    virtio_pstore_from_filename(s, dent->d_name, path, sizeof(path),
&info);
+    fd = open(path, O_RDONLY);
+    if (fd < 0) {
+        error_report("cannot open %s", path);
+        return -1;
+    }
+
+    if (fstat(fd, &stbuf) < 0) {
+        len = -1;
+        goto out;
+    }
+
+    len = readv(fd, sg, sg_num);
+    if (len < 0) {
+        if (errno == EAGAIN) {
+            len = 0;
+        }
+        goto out;
+    }
+
+    info.id        = cpu_to_le64(info.id);
+    info.type      = cpu_to_le16(info.type);
+    info.flags     = cpu_to_le32(info.flags);
+    info.len       = cpu_to_le32(len);
+    info.time_sec  = cpu_to_le64(stbuf.st_ctim.tv_sec);
+    info.time_nsec = cpu_to_le32(stbuf.st_ctim.tv_nsec);
+
+    iov_from_buf(in_sg, in_num, sizeof(*res), &info, sizeof(info));
+    len += sizeof(info);
+
+ out:
+    close(fd);
+    return len;
+}
+
+static ssize_t virtio_pstore_do_write(VirtIOPstore *s, struct iovec *out_sg,
+                                      unsigned int out_num,
+                                      struct virtio_pstore_req *req)
+{
+    char path[PATH_MAX];
+    int fd;
+    ssize_t len;
+    unsigned short type;
+    int flags = O_WRONLY | O_CREAT;
+
+    /* we already consume the req */
+    iov_discard_front(&out_sg, &out_num, sizeof(*req));
+
+    virtio_pstore_to_filename(s, path, sizeof(path), req);
+
+    type = le16_to_cpu(req->type);
+
+    if (type == VIRTIO_PSTORE_TYPE_DMESG) {
+        flags |= O_TRUNC;
+    } else if (type == VIRTIO_PSTORE_TYPE_CONSOLE) {
+        flags |= O_APPEND;
+    }
+
+    fd = open(path, flags, 0644);
+    if (fd < 0) {
+        error_report("cannot open %s", path);
+        return -1;
+    }
+    len = writev(fd, out_sg, out_num);
+    close(fd);
+
+    return len;
+}
+
+static ssize_t virtio_pstore_do_close(VirtIOPstore *s)
+{
+    if (s->dirp == NULL) {
+        return 0;
+    }
+
+    closedir(s->dirp);
+    s->dirp = NULL;
+
+    return 0;
+}
+
+static ssize_t virtio_pstore_do_erase(VirtIOPstore *s,
+                                      struct virtio_pstore_req *req)
+{
+    char path[PATH_MAX];
+
+    virtio_pstore_to_filename(s, path, sizeof(path), req);
+
+    return unlink(path);
+}
+
+static void virtio_pstore_handle_io(VirtIODevice *vdev, VirtQueue *vq)
+{
+    VirtIOPstore *s = VIRTIO_PSTORE(vdev);
+    VirtQueueElement *elem;
+    struct virtio_pstore_req req;
+    struct virtio_pstore_res res;
+    ssize_t len = 0;
+    int ret;
+
+    for (;;) {
+        elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
+        if (!elem) {
+            return;
+        }
+
+        if (elem->out_num < 1 || elem->in_num < 1) {
+            error_report("request or response buffer is missing");
+            exit(1);
+        }
+
+        len = iov_to_buf(elem->out_sg, elem->out_num, 0, &req,
sizeof(req));
+        if (len != (ssize_t)sizeof(req)) {
+            error_report("invalid request size: %ld", (long)len);
+            exit(1);
+        }
+        res.cmd  = req.cmd;
+        res.type = req.type;
+
+        switch (le16_to_cpu(req.cmd)) {
+        case VIRTIO_PSTORE_CMD_OPEN:
+            ret = virtio_pstore_do_open(s);
+            break;
+        case VIRTIO_PSTORE_CMD_READ:
+            ret = virtio_pstore_do_read(s, elem->in_sg, elem->in_num,
&res);
+            if (ret > 0) {
+                len = ret;
+                ret = 0;
+            }
+            break;
+        case VIRTIO_PSTORE_CMD_WRITE:
+            ret = virtio_pstore_do_write(s, elem->out_sg, elem->out_num,
&req);
+            break;
+        case VIRTIO_PSTORE_CMD_CLOSE:
+            ret = virtio_pstore_do_close(s);
+            break;
+        case VIRTIO_PSTORE_CMD_ERASE:
+            ret = virtio_pstore_do_erase(s, &req);
+            break;
+        default:
+            ret = -1;
+            break;
+        }
+
+        res.ret  = ret;
+
+        iov_from_buf(elem->in_sg, elem->in_num, 0, &res,
sizeof(res));
+        virtqueue_push(vq, elem, sizeof(res) + len);
+
+        virtio_notify(vdev, vq);
+        g_free(elem);
+
+        if (ret < 0) {
+            return;
+        }
+    }
+}
+
+static void virtio_pstore_device_realize(DeviceState *dev, Error **errp)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VirtIOPstore *s = VIRTIO_PSTORE(dev);
+
+    virtio_init(vdev, "virtio-pstore", VIRTIO_ID_PSTORE,
+                sizeof(struct virtio_pstore_config));
+
+    s->id = 1;
+    s->console_id = 0;
+
+    s->vq[0] = virtio_add_queue(vdev, 128, virtio_pstore_handle_io);
+    s->vq[1] = virtio_add_queue(vdev, 128, virtio_pstore_handle_io);
+}
+
+static void virtio_pstore_device_unrealize(DeviceState *dev, Error **errp)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+
+    virtio_cleanup(vdev);
+}
+
+static void virtio_pstore_get_config(VirtIODevice *vdev, uint8_t *config_data)
+{
+    VirtIOPstore *dev = VIRTIO_PSTORE(vdev);
+    struct virtio_pstore_config config;
+
+    config.bufsize = cpu_to_le32(dev->bufsize);
+    if (dev->console) {
+        config.flags |= cpu_to_le32(VIRTIO_PSTORE_CONFIG_FL_CONSOLE);
+    }
+
+    memcpy(config_data, &config, sizeof(struct virtio_pstore_config));
+}
+
+static void virtio_pstore_set_config(VirtIODevice *vdev,
+                                     const uint8_t *config_data)
+{
+    VirtIOPstore *dev = VIRTIO_PSTORE(vdev);
+    struct virtio_pstore_config config;
+
+    memcpy(&config, config_data, sizeof(struct virtio_pstore_config));
+
+    dev->bufsize = le32_to_cpu(config.bufsize);
+}
+
+static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
+{
+    return f;
+}
+
+static void pstore_get_directory(Object *obj, Visitor *v,
+                                 const char *name, void *opaque,
+                                 Error **errp)
+{
+    VirtIOPstore *s = opaque;
+
+    visit_type_str(v, name, &s->directory, errp);
+}
+
+static void pstore_set_directory(Object *obj, Visitor *v,
+                                 const char *name, void *opaque,
+                                 Error **errp)
+{
+    VirtIOPstore *s = opaque;
+    Error *local_err = NULL;
+    char *value;
+
+    visit_type_str(v, name, &value, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    g_free(s->directory);
+    s->directory = value;
+}
+
+static void pstore_release_directory(Object *obj, const char *name,
+                                     void *opaque)
+{
+    VirtIOPstore *s = opaque;
+
+    g_free(s->directory);
+    s->directory = NULL;
+}
+
+static void pstore_get_bufsize(Object *obj, Visitor *v,
+                               const char *name, void *opaque,
+                               Error **errp)
+{
+    VirtIOPstore *s = opaque;
+    uint64_t value = s->bufsize;
+
+    visit_type_size(v, name, &value, errp);
+}
+
+static void pstore_set_bufsize(Object *obj, Visitor *v,
+                               const char *name, void *opaque,
+                               Error **errp)
+{
+    VirtIOPstore *s = opaque;
+    Error *error = NULL;
+    uint64_t value;
+
+    visit_type_size(v, name, &value, &error);
+    if (error) {
+        error_propagate(errp, error);
+        return;
+    }
+
+    if (value < 4096) {
+        error_report("Warning: too small buffer size: %"PRIu64,
value);
+    }
+
+    s->bufsize = value;
+}
+
+static void pstore_get_console(Object *obj, Visitor *v,
+                               const char *name, void *opaque,
+                               Error **errp)
+{
+    VirtIOPstore *s = opaque;
+    bool value = s->console;
+
+    visit_type_bool(v, name, &value, errp);
+}
+
+static void pstore_set_console(Object *obj, Visitor *v,
+                               const char *name, void *opaque,
+                               Error **errp)
+{
+    VirtIOPstore *s = opaque;
+    Error *error = NULL;
+    bool value;
+
+    visit_type_bool(v, name, &value, &error);
+    if (error) {
+        error_propagate(errp, error);
+        return;
+    }
+
+    s->console = value;
+}
+
+static Property virtio_pstore_properties[] = {
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void virtio_pstore_instance_init(Object *obj)
+{
+    VirtIOPstore *s = VIRTIO_PSTORE(obj);
+
+    object_property_add(obj, "directory", "str",
+                        pstore_get_directory, pstore_set_directory,
+                        pstore_release_directory, s, NULL);
+    object_property_add(obj, "bufsize", "size",
+                        pstore_get_bufsize, pstore_set_bufsize, NULL, s, NULL);
+    object_property_add(obj, "console", "bool",
+                        pstore_get_console, pstore_set_console, NULL, s, NULL);
+}
+
+static void virtio_pstore_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
+
+    dc->props = virtio_pstore_properties;
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+    vdc->realize = virtio_pstore_device_realize;
+    vdc->unrealize = virtio_pstore_device_unrealize;
+    vdc->get_config = virtio_pstore_get_config;
+    vdc->set_config = virtio_pstore_set_config;
+    vdc->get_features = get_features;
+}
+
+static const TypeInfo virtio_pstore_info = {
+    .name = TYPE_VIRTIO_PSTORE,
+    .parent = TYPE_VIRTIO_DEVICE,
+    .instance_size = sizeof(VirtIOPstore),
+    .instance_init = virtio_pstore_instance_init,
+    .class_init = virtio_pstore_class_init,
+};
+
+static void virtio_register_types(void)
+{
+    type_register_static(&virtio_pstore_info);
+}
+
+type_init(virtio_register_types)
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index 74d797d..000e1e9 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -79,6 +79,7 @@
 #define PCI_DEVICE_ID_VIRTIO_SCSI        0x1004
 #define PCI_DEVICE_ID_VIRTIO_RNG         0x1005
 #define PCI_DEVICE_ID_VIRTIO_9P          0x1009
+#define PCI_DEVICE_ID_VIRTIO_PSTORE      0x100a
 
 #define PCI_VENDOR_ID_REDHAT             0x1b36
 #define PCI_DEVICE_ID_REDHAT_BRIDGE      0x0001
diff --git a/include/hw/virtio/virtio-pstore.h
b/include/hw/virtio/virtio-pstore.h
new file mode 100644
index 0000000..d188a48
--- /dev/null
+++ b/include/hw/virtio/virtio-pstore.h
@@ -0,0 +1,34 @@
+/*
+ * Virtio Pstore Support
+ *
+ * Authors:
+ *  Namhyung Kim      <namhyung at gmail.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef _QEMU_VIRTIO_PSTORE_H
+#define _QEMU_VIRTIO_PSTORE_H
+
+#include "standard-headers/linux/virtio_pstore.h"
+#include "hw/virtio/virtio.h"
+#include "hw/pci/pci.h"
+
+#define TYPE_VIRTIO_PSTORE "virtio-pstore-device"
+#define VIRTIO_PSTORE(obj) \
+        OBJECT_CHECK(VirtIOPstore, (obj), TYPE_VIRTIO_PSTORE)
+
+typedef struct VirtIOPstore {
+    VirtIODevice    parent_obj;
+    VirtQueue      *vq[2];
+    char           *directory;
+    uint64_t        id;
+    uint64_t        console_id;
+    DIR            *dirp;
+    uint64_t        bufsize;
+    bool            console;
+} VirtIOPstore;
+
+#endif
diff --git a/include/standard-headers/linux/virtio_ids.h
b/include/standard-headers/linux/virtio_ids.h
index 77925f5..c72a9ab 100644
--- a/include/standard-headers/linux/virtio_ids.h
+++ b/include/standard-headers/linux/virtio_ids.h
@@ -41,5 +41,6 @@
 #define VIRTIO_ID_CAIF	       12 /* Virtio caif */
 #define VIRTIO_ID_GPU          16 /* virtio GPU */
 #define VIRTIO_ID_INPUT        18 /* virtio input */
+#define VIRTIO_ID_PSTORE       22 /* virtio pstore */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
diff --git a/include/standard-headers/linux/virtio_pstore.h
b/include/standard-headers/linux/virtio_pstore.h
new file mode 100644
index 0000000..b893d15
--- /dev/null
+++ b/include/standard-headers/linux/virtio_pstore.h
@@ -0,0 +1,80 @@
+#ifndef _LINUX_VIRTIO_PSTORE_H
+#define _LINUX_VIRTIO_PSTORE_H
+/* This header is BSD licensed so anyone can use the definitions to implement
+ * compatible drivers/servers.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of IBM nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE. */
+#include "standard-headers/linux/types.h"
+#include "standard-headers/linux/virtio_types.h"
+#include "standard-headers/linux/virtio_ids.h"
+#include "standard-headers/linux/virtio_config.h"
+
+#define VIRTIO_PSTORE_CMD_NULL   0
+#define VIRTIO_PSTORE_CMD_OPEN   1
+#define VIRTIO_PSTORE_CMD_READ   2
+#define VIRTIO_PSTORE_CMD_WRITE  3
+#define VIRTIO_PSTORE_CMD_ERASE  4
+#define VIRTIO_PSTORE_CMD_CLOSE  5
+
+#define VIRTIO_PSTORE_TYPE_UNKNOWN  0
+#define VIRTIO_PSTORE_TYPE_DMESG    1
+#define VIRTIO_PSTORE_TYPE_CONSOLE  2
+
+#define VIRTIO_PSTORE_FL_COMPRESSED  1
+
+#define VIRTIO_PSTORE_CONFIG_FL_CONSOLE  (1 << 0)
+
+struct virtio_pstore_req {
+    __virtio16 cmd;
+    __virtio16 type;
+    __virtio32 flags;
+    __virtio64 id;
+    __virtio32 count;
+    __virtio32 reserved;
+};
+
+struct virtio_pstore_res {
+    __virtio16 cmd;
+    __virtio16 type;
+    __virtio32 ret;
+};
+
+struct virtio_pstore_fileinfo {
+    __virtio64 id;
+    __virtio32 count;
+    __virtio16 type;
+    __virtio16 unused;
+    __virtio32 flags;
+    __virtio32 len;
+    __virtio64 time_sec;
+    __virtio32 time_nsec;
+    __virtio32 reserved;
+};
+
+struct virtio_pstore_config {
+    __virtio32 bufsize;
+    __virtio32 flags;
+};
+
+#endif /* _LINUX_VIRTIO_PSTORE_H */
diff --git a/qdev-monitor.c b/qdev-monitor.c
index e19617f..e1df5a9 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -73,6 +73,7 @@ static const QDevAlias qdev_alias_table[] = {
     { "virtio-serial-pci", "virtio-serial", QEMU_ARCH_ALL
& ~QEMU_ARCH_S390X },
     { "virtio-tablet-ccw", "virtio-tablet", QEMU_ARCH_S390X
},
     { "virtio-tablet-pci", "virtio-tablet", QEMU_ARCH_ALL
& ~QEMU_ARCH_S390X },
+    { "virtio-pstore-pci", "virtio-pstore" },
     { }
 };
 
-- 
2.8.0

Add virtio pstore device to allow kernel log messages saved on the
host.  With this patch, it will save the log files under directory given
by --pstore option.

  $ lkvm run --pstore=dir-xx

  (guest) # echo c > /proc/sysrq-trigger

  $ ls dir-xx
  dmesg-1.enc.z  dmesg-2.enc.z

The log files are usually compressed using zlib.  User can easily see
the messages on the host or on the guest (using pstore filesystem).

Cc: Anton Vorontsov <anton at enomsg.org>
Cc: Colin Cross <ccross at android.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Steven Rostedt <rostedt at goodmis.org>
Cc: Ingo Molnar <mingo at kernel.org>
Cc: Will Deacon <will.deacon at arm.com>
Signed-off-by: Namhyung Kim <namhyung at kernel.org>
---
 Makefile                     |   1 +
 builtin-run.c                |   2 +
 include/kvm/kvm-config.h     |   1 +
 include/kvm/virtio-pci-dev.h |   2 +
 include/kvm/virtio-pstore.h  |  57 ++++++
 include/linux/virtio_ids.h   |   1 +
 virtio/pstore.c              | 459 +++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 523 insertions(+)
 create mode 100644 include/kvm/virtio-pstore.h
 create mode 100644 virtio/pstore.c

diff --git a/Makefile b/Makefile
index 1f0196f..d7462b9 100644
--- a/Makefile
+++ b/Makefile
@@ -67,6 +67,7 @@ OBJS	+= virtio/net.o
 OBJS	+= virtio/rng.o
 OBJS    += virtio/balloon.o
 OBJS	+= virtio/pci.o
+OBJS	+= virtio/pstore.o
 OBJS	+= disk/blk.o
 OBJS	+= disk/qcow.o
 OBJS	+= disk/raw.o
diff --git a/builtin-run.c b/builtin-run.c
index 72b878d..08c12dd 100644
--- a/builtin-run.c
+++ b/builtin-run.c
@@ -128,6 +128,8 @@ void kvm_run_set_wrapper_sandbox(void)
 			" rootfs"),					\
 	OPT_STRING('\0', "hugetlbfs", &(cfg)->hugetlbfs_path,
"path",	\
 			"Hugetlbfs path"),				\
+	OPT_STRING('\0', "pstore", &(cfg)->pstore_path,
"path",		\
+			"pstore data path"),				\
 									\
 	OPT_GROUP("Kernel options:"),					\
 	OPT_STRING('k', "kernel", &(cfg)->kernel_filename,
"kernel",	\
diff --git a/include/kvm/kvm-config.h b/include/kvm/kvm-config.h
index 386fa8c..42b7651 100644
--- a/include/kvm/kvm-config.h
+++ b/include/kvm/kvm-config.h
@@ -45,6 +45,7 @@ struct kvm_config {
 	const char *hugetlbfs_path;
 	const char *custom_rootfs_name;
 	const char *real_cmdline;
+	const char *pstore_path;
 	struct virtio_net_params *net_params;
 	bool single_step;
 	bool vnc;
diff --git a/include/kvm/virtio-pci-dev.h b/include/kvm/virtio-pci-dev.h
index 48ae018..4339d94 100644
--- a/include/kvm/virtio-pci-dev.h
+++ b/include/kvm/virtio-pci-dev.h
@@ -15,6 +15,7 @@
 #define PCI_DEVICE_ID_VIRTIO_BLN		0x1005
 #define PCI_DEVICE_ID_VIRTIO_SCSI		0x1008
 #define PCI_DEVICE_ID_VIRTIO_9P			0x1009
+#define PCI_DEVICE_ID_VIRTIO_PSTORE		0x100a
 #define PCI_DEVICE_ID_VESA			0x2000
 #define PCI_DEVICE_ID_PCI_SHMEM			0x0001
 
@@ -34,5 +35,6 @@
 #define PCI_CLASS_RNG				0xff0000
 #define PCI_CLASS_BLN				0xff0000
 #define PCI_CLASS_9P				0xff0000
+#define PCI_CLASS_PSTORE			0xff0000
 
 #endif /* VIRTIO_PCI_DEV_H_ */
diff --git a/include/kvm/virtio-pstore.h b/include/kvm/virtio-pstore.h
new file mode 100644
index 0000000..670d5e3
--- /dev/null
+++ b/include/kvm/virtio-pstore.h
@@ -0,0 +1,57 @@
+#ifndef KVM__PSTORE_VIRTIO_H
+#define KVM__PSTORE_VIRTIO_H
+
+#include <kvm/virtio.h>
+#include <sys/types.h>
+
+#define VIRTIO_PSTORE_CMD_NULL   0
+#define VIRTIO_PSTORE_CMD_OPEN   1
+#define VIRTIO_PSTORE_CMD_READ   2
+#define VIRTIO_PSTORE_CMD_WRITE  3
+#define VIRTIO_PSTORE_CMD_ERASE  4
+#define VIRTIO_PSTORE_CMD_CLOSE  5
+
+#define VIRTIO_PSTORE_TYPE_UNKNOWN  0
+#define VIRTIO_PSTORE_TYPE_DMESG    1
+#define VIRTIO_PSTORE_TYPE_CONSOLE  2
+
+#define VIRTIO_PSTORE_FL_COMPRESSED  1
+
+#define VIRTIO_PSTORE_CONFIG_FL_CONSOLE  (1 << 0)
+
+struct virtio_pstore_req {
+	__virtio16		cmd;
+	__virtio16		type;
+	__virtio32		flags;
+	__virtio64		id;
+	__virtio32		count;
+	__virtio32		reserved;
+};
+
+struct virtio_pstore_res {
+	__virtio16		cmd;
+	__virtio16		type;
+	__virtio32		ret;
+};
+
+struct virtio_pstore_fileinfo {
+	__virtio64		id;
+	__virtio32		count;
+	__virtio16		type;
+	__virtio16		unused;
+	__virtio32		flags;
+	__virtio32		len;
+	__virtio64		time_sec;
+	__virtio32		time_nsec;
+	__virtio32		reserved;
+};
+
+struct virtio_pstore_config {
+	__virtio32		bufsize;
+	__virtio32		flags;
+};
+
+int virtio_pstore__init(struct kvm *kvm);
+int virtio_pstore__exit(struct kvm *kvm);
+
+#endif /* KVM__PSTORE_VIRTIO_H */
diff --git a/include/linux/virtio_ids.h b/include/linux/virtio_ids.h
index 5f60aa4..40eabf7 100644
--- a/include/linux/virtio_ids.h
+++ b/include/linux/virtio_ids.h
@@ -40,5 +40,6 @@
 #define VIRTIO_ID_RPROC_SERIAL 11 /* virtio remoteproc serial link */
 #define VIRTIO_ID_CAIF	       12 /* Virtio caif */
 #define VIRTIO_ID_INPUT        18 /* virtio input */
+#define VIRTIO_ID_PSTORE       22 /* virtio pstore */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
diff --git a/virtio/pstore.c b/virtio/pstore.c
new file mode 100644
index 0000000..8290c14
--- /dev/null
+++ b/virtio/pstore.c
@@ -0,0 +1,459 @@
+#include "kvm/virtio-pstore.h"
+
+#include "kvm/virtio-pci-dev.h"
+
+#include "kvm/virtio.h"
+#include "kvm/util.h"
+#include "kvm/kvm.h"
+#include "kvm/threadpool.h"
+#include "kvm/guest_compat.h"
+
+#include <linux/virtio_ring.h>
+
+#include <linux/list.h>
+#include <fcntl.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <pthread.h>
+#include <linux/kernel.h>
+#include <sys/eventfd.h>
+
+#define NUM_VIRT_QUEUES			2
+#define VIRTIO_PSTORE_QUEUE_SIZE	128
+
+struct io_thread_arg {
+	struct kvm		*kvm;
+	struct pstore_dev	*pdev;
+};
+
+struct pstore_dev {
+	struct list_head	list;
+	struct virtio_device	vdev;
+	pthread_t		io_thread;
+	int			io_efd;
+	int			done;
+
+	struct virtio_pstore_config *config;
+
+	int			fd;
+	DIR			*dir;
+	u64			id;
+	u64			console_id;
+
+	/* virtio queue */
+	struct virt_queue	vqs[NUM_VIRT_QUEUES];
+};
+
+static LIST_HEAD(pdevs);
+static int compat_id = -1;
+
+static u8 *get_config(struct kvm *kvm, void *dev)
+{
+	struct pstore_dev *pdev = dev;
+
+	return (u8*)pdev->config;
+}
+
+static u32 get_host_features(struct kvm *kvm, void *dev)
+{
+	/* Unused */
+	return 0;
+}
+
+static void set_guest_features(struct kvm *kvm, void *dev, u32 features)
+{
+	/* Unused */
+}
+
+static void virtio_pstore_to_filename(struct kvm *kvm, struct pstore_dev *pdev,
+				      char *buf, size_t sz,
+				      struct virtio_pstore_req *req)
+{
+	const char *basename;
+	unsigned long long id = 0;
+	unsigned int flags = virtio_host_to_guest_u64(pdev->vqs, req->flags);
+
+	switch (req->type) {
+	case VIRTIO_PSTORE_TYPE_DMESG:
+		basename = "dmesg";
+		id = pdev->id++;
+		break;
+	case VIRTIO_PSTORE_TYPE_CONSOLE:
+		basename = "console";
+		if (pdev->console_id)
+			id = pdev->console_id;
+		else
+			id = pdev->console_id = pdev->id++;
+		break;
+	default:
+		basename = "unknown";
+		break;
+	}
+
+	snprintf(buf, sz, "%s/%s-%llu%s", kvm->cfg.pstore_path, basename,
id,
+		 flags & VIRTIO_PSTORE_FL_COMPRESSED ? ".enc.z" :
"");
+}
+
+static void virtio_pstore_from_filename(struct kvm *kvm, char *name,
+					char *buf, size_t sz,
+					struct virtio_pstore_fileinfo *info)
+{
+	size_t len = strlen(name);
+
+	snprintf(buf, sz, "%s/%s", kvm->cfg.pstore_path, name);
+
+	info->flags = 0;
+	if (len > 6 && !strncmp(name + len - 6, ".enc.z", 6))
+		info->flags |= VIRTIO_PSTORE_FL_COMPRESSED;
+
+	if (!strncmp(name, "dmesg-", 6)) {
+		info->type = VIRTIO_PSTORE_TYPE_DMESG;
+		name += strlen("dmesg-");
+	} else if (!strncmp(name, "console-", 8)) {
+		info->type = VIRTIO_PSTORE_TYPE_CONSOLE;
+		name += strlen("console-");
+	} else if (!strncmp(name, "unknown-", 8)) {
+		info->type = VIRTIO_PSTORE_TYPE_UNKNOWN;
+		name += strlen("unknown-");
+	}
+
+	info->id = strtoul(name, NULL, 0);
+}
+
+static int virtio_pstore_do_open(struct kvm *kvm, struct pstore_dev *pdev,
+				 struct virtio_pstore_req *req,
+				 struct iovec *iov)
+{
+	pdev->dir = opendir(kvm->cfg.pstore_path);
+	if (pdev->dir == NULL)
+		return -errno;
+
+	return 0;
+}
+
+static int virtio_pstore_do_close(struct kvm *kvm, struct pstore_dev *pdev,
+				  struct virtio_pstore_req *req,
+				  struct iovec *iov)
+{
+	if (pdev->dir == NULL)
+		return -1;
+
+	closedir(pdev->dir);
+	pdev->dir = NULL;
+
+	return 0;
+}
+
+static ssize_t virtio_pstore_do_read(struct kvm *kvm, struct pstore_dev *pdev,
+				     struct virtio_pstore_req *req,
+				     struct iovec *iov,
+				     struct virtio_pstore_fileinfo *info)
+{
+	char path[PATH_MAX];
+	FILE *fp;
+	ssize_t len = 0;
+	struct stat stbuf;
+	struct dirent *dent;
+
+	if (pdev->dir == NULL)
+		return 0;
+
+	dent = readdir(pdev->dir);
+	while (dent) {
+		if (dent->d_name[0] != '.')
+			break;
+		dent = readdir(pdev->dir);
+	}
+
+	if (dent == NULL)
+		return 0;
+
+	virtio_pstore_from_filename(kvm, dent->d_name, path, sizeof(path), info);
+	fp = fopen(path, "r");
+	if (fp == NULL)
+		return -1;
+
+	if (fstat(fileno(fp), &stbuf) < 0)
+		return -1;
+
+	len = fread(iov[3].iov_base, 1, iov[3].iov_len, fp);
+	if (len < 0 && errno == EAGAIN) {
+		len = 0;
+		goto out;
+	}
+
+	info->id     = virtio_host_to_guest_u64(pdev->vqs, info->id);
+	info->type   = virtio_host_to_guest_u64(pdev->vqs, info->type);
+	info->flags  = virtio_host_to_guest_u32(pdev->vqs, info->flags);
+	info->len    = virtio_host_to_guest_u32(pdev->vqs, len);
+
+	info->time_sec  = virtio_host_to_guest_u64(pdev->vqs,
stbuf.st_ctim.tv_sec);
+	info->time_nsec = virtio_host_to_guest_u32(pdev->vqs,
stbuf.st_ctim.tv_nsec);
+
+	len += sizeof(*info);
+
+out:
+	fclose(fp);
+	return len;
+}
+
+static ssize_t virtio_pstore_do_write(struct kvm *kvm, struct pstore_dev *pdev,
+				      struct virtio_pstore_req *req,
+				      struct iovec *iov)
+{
+	char path[PATH_MAX];
+	FILE *fp;
+	ssize_t len = 0;
+
+	virtio_pstore_to_filename(kvm, pdev, path, sizeof(path), req);
+
+	fp = fopen(path, "a");
+	if (fp == NULL)
+		return -1;
+
+	len = fwrite(iov[1].iov_base, 1, iov[1].iov_len, fp);
+	if (len < 0 && errno == EAGAIN)
+		len = 0;
+
+	fclose(fp);
+	return 0;
+}
+
+static ssize_t virtio_pstore_do_erase(struct kvm *kvm, struct pstore_dev *pdev,
+				      struct virtio_pstore_req *req,
+				      struct iovec *iov)
+{
+	char path[PATH_MAX];
+
+	virtio_pstore_to_filename(kvm, pdev, path, sizeof(path), req);
+
+	return unlink(path);
+}
+
+static bool virtio_pstore_do_io_request(struct kvm *kvm, struct pstore_dev
*pdev,
+					struct virt_queue *vq)
+{
+	struct iovec iov[VIRTIO_PSTORE_QUEUE_SIZE];
+	struct virtio_pstore_req *req;
+	struct virtio_pstore_res *res;
+	struct virtio_pstore_fileinfo *info;
+	ssize_t len = 0;
+	u16 out, in, head;
+	int ret = 0;
+
+	head = virt_queue__get_iov(vq, iov, &out, &in, kvm);
+
+	if (iov[0].iov_len != sizeof(*req) || iov[out].iov_len != sizeof(*res)) {
+		return false;
+	}
+
+	req = iov[0].iov_base;
+	res = iov[out].iov_base;
+
+	switch (virtio_guest_to_host_u16(vq, req->cmd)) {
+	case VIRTIO_PSTORE_CMD_OPEN:
+		ret = virtio_pstore_do_open(kvm, pdev, req, iov);
+		break;
+	case VIRTIO_PSTORE_CMD_READ:
+		info = iov[out + 1].iov_base;
+		ret = virtio_pstore_do_read(kvm, pdev, req, iov, info);
+		if (ret > 0) {
+			len = ret;
+			ret = 0;
+		}
+		break;
+	case VIRTIO_PSTORE_CMD_WRITE:
+		ret = virtio_pstore_do_write(kvm, pdev, req, iov);
+		break;
+	case VIRTIO_PSTORE_CMD_CLOSE:
+		ret = virtio_pstore_do_close(kvm, pdev, req, iov);
+		break;
+	case VIRTIO_PSTORE_CMD_ERASE:
+		ret = virtio_pstore_do_erase(kvm, pdev, req, iov);
+		break;
+	default:
+		return false;
+	}
+
+	res->cmd  = req->cmd;
+	res->type = req->type;
+	res->ret  = virtio_host_to_guest_u32(vq, ret);
+
+	virt_queue__set_used_elem(vq, head, sizeof(*res) + len);
+
+	return ret == 0;
+}
+
+static void virtio_pstore_do_io(struct kvm *kvm, struct pstore_dev *pdev,
+				struct virt_queue *vq)
+{
+	bool done = false;
+
+	while (virt_queue__available(vq)) {
+		virtio_pstore_do_io_request(kvm, pdev, vq);
+		done = true;
+	}
+
+	if (done)
+		pdev->vdev.ops->signal_vq(kvm, &pdev->vdev, vq - pdev->vqs);
+}
+
+static void *virtio_pstore_io_thread(void *arg)
+{
+	struct io_thread_arg *io_arg = arg;
+	struct pstore_dev *pdev = io_arg->pdev;
+	struct kvm *kvm = io_arg->kvm;
+	u64 data;
+	int r;
+
+	kvm__set_thread_name("virtio-pstore-io");
+
+	while (!pdev->done) {
+		r = read(pdev->io_efd, &data, sizeof(u64));
+		if (r < 0)
+			continue;
+
+		virtio_pstore_do_io(kvm, pdev, &pdev->vqs[0]);
+		virtio_pstore_do_io(kvm, pdev, &pdev->vqs[1]);
+	}
+	free(io_arg);
+
+	pthread_exit(NULL);
+	return NULL;
+}
+
+static int init_vq(struct kvm *kvm, void *dev, u32 vq, u32 page_size, u32
align,
+		   u32 pfn)
+{
+	struct pstore_dev *pdev = dev;
+	struct virt_queue *queue;
+	void *p;
+
+	compat__remove_message(compat_id);
+
+	queue		= &pdev->vqs[vq];
+	queue->pfn	= pfn;
+	p		= virtio_get_vq(kvm, queue->pfn, page_size);
+
+	vring_init(&queue->vring, VIRTIO_PSTORE_QUEUE_SIZE, p, align);
+
+	return 0;
+}
+
+static int notify_vq(struct kvm *kvm, void *dev, u32 vq)
+{
+	struct pstore_dev *pdev = dev;
+	u64 data = 1;
+	int r;
+
+	r = write(pdev->io_efd, &data, sizeof(data));
+	if (r < 0)
+		return r;
+
+	return 0;
+}
+
+static int get_pfn_vq(struct kvm *kvm, void *dev, u32 vq)
+{
+	struct pstore_dev *pdev = dev;
+
+	return pdev->vqs[vq].pfn;
+}
+
+static int get_size_vq(struct kvm *kvm, void *dev, u32 vq)
+{
+	return VIRTIO_PSTORE_QUEUE_SIZE;
+}
+
+static int set_size_vq(struct kvm *kvm, void *dev, u32 vq, int size)
+{
+	/* FIXME: dynamic */
+	return size;
+}
+
+static struct virtio_ops pstore_dev_virtio_ops = {
+	.get_config		= get_config,
+	.get_host_features	= get_host_features,
+	.set_guest_features	= set_guest_features,
+	.init_vq		= init_vq,
+	.notify_vq		= notify_vq,
+	.get_pfn_vq		= get_pfn_vq,
+	.get_size_vq		= get_size_vq,
+	.set_size_vq		= set_size_vq,
+};
+
+int virtio_pstore__init(struct kvm *kvm)
+{
+	struct pstore_dev *pdev;
+	struct io_thread_arg *io_arg = NULL;
+	int r;
+
+	if (!kvm->cfg.pstore_path)
+		return 0;
+
+	pdev = calloc(1, sizeof(*pdev));
+	if (pdev == NULL)
+		return -ENOMEM;
+
+	pdev->config = calloc(1, sizeof(*pdev->config));
+	if (pdev->config == NULL) {
+		r = -ENOMEM;
+		goto cleanup;
+	}
+
+	pdev->id = 1;
+	pdev->console_id = 0;
+
+	io_arg = malloc(sizeof(*io_arg));
+	if (io_arg == NULL) {
+		r = -ENOMEM;
+		goto cleanup;
+	}
+
+	pdev->io_efd = eventfd(0, 0);
+
+	*io_arg = (struct io_thread_arg) {
+		.pdev   = pdev,
+		.kvm    = kvm,
+	};
+	r = pthread_create(&pdev->io_thread, NULL,
+			   virtio_pstore_io_thread, io_arg);
+	if (r < 0)
+		goto cleanup;
+
+	r = virtio_init(kvm, pdev, &pdev->vdev, &pstore_dev_virtio_ops,
+			VIRTIO_DEFAULT_TRANS(kvm), PCI_DEVICE_ID_VIRTIO_PSTORE,
+			VIRTIO_ID_PSTORE, PCI_CLASS_PSTORE);
+	if (r < 0)
+		goto cleanup;
+
+	list_add_tail(&pdev->list, &pdevs);
+
+	if (compat_id == -1)
+		compat_id = virtio_compat_add_message("virtio-pstore",
"CONFIG_VIRTIO_PSTORE");
+	return 0;
+
+cleanup:
+	free(io_arg);
+	free(pdev->config);
+	free(pdev);
+
+	return r;
+}
+virtio_dev_init(virtio_pstore__init);
+
+int virtio_pstore__exit(struct kvm *kvm)
+{
+	struct pstore_dev *pdev, *tmp;
+
+	list_for_each_entry_safe(pdev, tmp, &pdevs, list) {
+		list_del(&pdev->list);
+		close(pdev->io_efd);
+		pdev->vdev.ops->exit(kvm, &pdev->vdev);
+		free(pdev);
+	}
+
+	return 0;
+}
+virtio_dev_exit(virtio_pstore__exit);
-- 
2.8.0

On Thu, Jul 28, 2016 at 12:08:24AM +0900, Namhyung Kim
wrote:
> Hello,
> 
> This is v2 of the virtio-pstore work.  In this patchset I addressed
> most of feedbacks from previous version.  Limiting disk size is not
> implemented yet.
For some reason, only parts of the patchset were received.
Pls post all patches to all lists.

If you are changing the virtio interface with host,
like a new device, they you must copy the virtio TC
so make sure there are no objections from there.

https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio#feedback


>  * changes in v2)
>   - update VIRTIO_ID_PSTORE to 22  (Cornelia, Stefan)
>   - make buffer size configurable  (Cornelia)
>   - support PSTORE_TYPE_CONSOLE  (Kees)
>   - use separate virtqueues for read and write
>   - support concurrent async write
>   - manage pstore (file) id in device side
>   - fix various mistakes in qemu device  (Stefan)
> 
> It started from the fact that dumping ftrace buffer at kernel
> oops/panic takes too much time.  Although there's a way to reduce the
> size of the original data, sometimes I want to have the information as
> many as possible.  Maybe kexec/kdump can solve this problem but it
> consumes some portion of guest memory so I'd like to avoid it.  And I
> know the qemu + crashtool can dump and analyze the whole guest memory
> including the ftrace buffer without wasting guest memory, but it adds
> one more layer and has some limitation as an out-of-tree tool like not
> being in sync with the kernel changes.
> 
> So I think it'd be great using the pstore interface to dump guest
> kernel data on the host.  One can read the data on the host directly
> or on the guest (at the next boot) using pstore filesystem as usual.
> While this patchset only implements dumping kernel log buffer, it can
> be extended to have ftrace buffer and probably some more..
> 
> The patch 0001-0003 are preparation for pstore to support virtio
> device which requires async write.  The patch 0004 implements virtio
> pstore driver.  It has two virt queue for (sync) read and (async)
> write, pstore buffer and io request and response structure.  The
> virtio_pstore_req struct is to give information about the current
> pstore operation.  The result will be written to the virtio_pstore_res
> struct.  For read operation it also uses virtio_pstore_fileinfo struct.
> 
> The patch 0005 adds support for PSTORE_TYPE_CONSOLE which was
> requested by Kees.  The console data is appended to a single file for
> now.
> 
> The patch 0006 and 0007 implement virtio-pstore legacy PCI device on
> qemu-kvm and kvmtool respectively.  I referenced virtio-baloon and
> virtio-rng implementations and I don't know whether kvmtool supports
> modern virtio 1.0+ spec.  Other transports might be supported later.
> 
> For example, using virtio-pstore on qemu looks like below:
> 
>   $ qemu-system-x86_64 -enable-kvm -device virtio-pstore,directory=xxx
> 
> When guest kernel gets panic the log messages will be saved under the
> xxx directory.
> 
>   $ ls xxx
>   dmesg-1.enc.z  dmesg-2.enc.z
> 
> As you can see the pstore subsystem compresses the log data using zlib
> (now supports lzo and lz4 too).  The data can be extracted with the
> following command:
> 
>   $ cat xxx/dmesg-1.enc.z | \
>   > python -c 'import sys, zlib;
print(zlib.decompress(sys.stdin.read()))'
>   Oops#1 Part1
>   <5>[    0.000000] Linux version 4.6.0kvm+ (namhyung at danjae) (gcc
version 5.3.0 (GCC) ) #145 SMP Mon Jul 18 10:22:45 KST 2016
>   <6>[    0.000000] Command line: root=/dev/vda console=ttyS0
>   <6>[    0.000000] x86/fpu: Legacy x87 FPU detected.
>   <6>[    0.000000] x86/fpu: Using 'eager' FPU context
switches.
>   <6>[    0.000000] e820: BIOS-provided physical RAM map:
>   <6>[    0.000000] BIOS-e820: [mem
0x0000000000000000-0x000000000009fbff] usable
>   <6>[    0.000000] BIOS-e820: [mem
0x000000000009fc00-0x000000000009ffff] reserved
>   <6>[    0.000000] BIOS-e820: [mem
0x00000000000f0000-0x00000000000fffff] reserved
>   <6>[    0.000000] BIOS-e820: [mem
0x0000000000100000-0x0000000007fddfff] usable
>   <6>[    0.000000] BIOS-e820: [mem
0x0000000007fde000-0x0000000007ffffff] reserved
>   <6>[    0.000000] BIOS-e820: [mem
0x00000000feffc000-0x00000000feffffff] reserved
>   <6>[    0.000000] BIOS-e820: [mem
0x00000000fffc0000-0x00000000ffffffff] reserved
>   <6>[    0.000000] NX (Execute Disable) protection: active
>   <6>[    0.000000] SMBIOS 2.8 present.
>   <7>[    0.000000] DMI: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
>   ...
> 
> To enable PSTORE_TYPE_CONSOLE, add 'console=true' to virtio-pstore
> device option.  Also 'bufsize' option can set different size for
> pstore buffer (default is 16K).  Maybe we can add a config option to
> control the compression later.
> 
> Currently the kvmtool doesn't support any options except the directory
> the pstore saves the logs.
> 
> 
> Namhyung Kim (7):
>   pstore: Split pstore fragile flags
>   pstore/ram: Set pstore flags dynamically
>   pstore: Manage buffer position for async write
>   virtio: Basic implementation of virtio pstore driver
>   virtio-pstore: Support PSTORE_TYPE_CONSOLE
>   qemu: Implement virtio-pstore device
>   kvmtool: Implement virtio-pstore device
> 
>  drivers/acpi/apei/erst.c             |   2 +-
>  drivers/firmware/efi/efi-pstore.c    |   4 +-
>  drivers/virtio/Kconfig               |  10 +
>  drivers/virtio/Makefile              |   1 +
>  drivers/virtio/virtio_pstore.c       | 421 +++++++++++++++++++++
>  fs/pstore/platform.c                 |  65 +++-
>  fs/pstore/ram.c                      |   8 +
>  include/linux/pstore.h               |   9 +-
>  include/uapi/linux/Kbuild            |   1 +
>  include/uapi/linux/virtio_ids.h      |   1 +
>  include/uapi/linux/virtio_pstore.h   |  78 +++-
>  11 files changed, 580 insertions(+), 20 deletions(-)
>  create mode 100644 drivers/virtio/virtio_pstore.c
>  create mode 100644 include/uapi/linux/virtio_pstore.h
> 
> 
> Cc: Paolo Bonzini <pbonzini at redhat.com>
> Cc: Radim Kr?m?? <rkrcmar at redhat.com>
> Cc: "Michael S. Tsirkin" <mst at redhat.com>
> Cc: Anthony Liguori <aliguori at amazon.com>
> Cc: Anton Vorontsov <anton at enomsg.org>
> Cc: Colin Cross <ccross at android.com>
> Cc: Kees Cook <keescook at chromium.org>
> Cc: Tony Luck <tony.luck at intel.com>
> Cc: Steven Rostedt <rostedt at goodmis.org>
> Cc: Ingo Molnar <mingo at kernel.org>
> Cc: Minchan Kim <minchan at kernel.org>
> Cc: Will Deacon <will.deacon at arm.com>
> Cc: kvm at vger.kernel.org
> Cc: qemu-devel at nongnu.org
> Cc: virtualization at lists.linux-foundation.org
> 
> Thanks,
> Namhyung
> 
> 
> -- 
> 2.8.0
> 
> _______________________________________________
> Virtualization mailing list
> Virtualization at lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization

On Thu, Jul 28, 2016 at 12:08:30AM +0900, Namhyung Kim
wrote:
> Add virtio pstore device to allow kernel log files saved on the host.
> It will save the log files on the directory given by pstore device
> option.
> 
>   $ qemu-system-x86_64 -device virtio-pstore,directory=dir-xx ...
> 
>   (guest) # echo c > /proc/sysrq-trigger
So if the point is handling system crashes, I suspect
virtio is the wrong protocol to use. ATM it's rather
elaborate for performance, it's likely not to work when
linux is crashing. I think you want something very very
simple that will still work when you crash. Like maybe
a serial device?
>   $ ls dir-xx
>   dmesg-1.enc.z  dmesg-2.enc.z
> 
> The log files are usually compressed using zlib.  Users can see the log
> messages directly on the host or on the guest (using pstore filesystem).
So this lacks all management tools that a regular storage device
has, and these are necessary if people are to use this
in production.

For example, some kind of provision for limiting the amount of host disk
this can consume seems called for. Rate-limiting disk writes
on host also seems necessary. Handling host disk errors always
propagates error to guest but an option to e.g. stop vm might
be useful to avoid corruption.
> 
> The 'directory' property is required for virtio-pstore device to
work.
> It also adds 'bufsize' and 'console' (boolean) properties.
No idea what these do. Seem to be RW by guest but have no effect
otherwise.

> Cc: Paolo Bonzini <pbonzini at redhat.com>
> Cc: Radim Kr?m?? <rkrcmar at redhat.com>
> Cc: "Michael S. Tsirkin" <mst at redhat.com>
> Cc: Anthony Liguori <aliguori at amazon.com>
> Cc: Anton Vorontsov <anton at enomsg.org>
> Cc: Colin Cross <ccross at android.com>
> Cc: Kees Cook <keescook at chromium.org>
> Cc: Tony Luck <tony.luck at intel.com>
> Cc: Steven Rostedt <rostedt at goodmis.org>
> Cc: Ingo Molnar <mingo at kernel.org>
> Cc: Minchan Kim <minchan at kernel.org>
> Cc: kvm at vger.kernel.org
> Cc: qemu-devel at nongnu.org
> Cc: virtualization at lists.linux-foundation.org
> Signed-off-by: Namhyung Kim <namhyung at kernel.org>
> ---
>  hw/virtio/Makefile.objs                        |   2 +-
>  hw/virtio/virtio-pci.c                         |  54 +++
>  hw/virtio/virtio-pci.h                         |  14 +
>  hw/virtio/virtio-pstore.c                      | 477
+++++++++++++++++++++++++
>  include/hw/pci/pci.h                           |   1 +
>  include/hw/virtio/virtio-pstore.h              |  34 ++
>  include/standard-headers/linux/virtio_ids.h    |   1 +
>  include/standard-headers/linux/virtio_pstore.h |  80 +++++
>  qdev-monitor.c                                 |   1 +
>  9 files changed, 663 insertions(+), 1 deletion(-)
>  create mode 100644 hw/virtio/virtio-pstore.c
>  create mode 100644 include/hw/virtio/virtio-pstore.h
>  create mode 100644 include/standard-headers/linux/virtio_pstore.h
> 
> diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
> index 3e2b175..aae7082 100644
> --- a/hw/virtio/Makefile.objs
> +++ b/hw/virtio/Makefile.objs
> @@ -4,4 +4,4 @@ common-obj-y += virtio-bus.o
>  common-obj-y += virtio-mmio.o
>  
>  obj-y += virtio.o virtio-balloon.o 
> -obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
> +obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
virtio-pstore.o
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index f0677b7..d99a405 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -2414,6 +2414,59 @@ static const TypeInfo virtio_host_pci_info = {
>  };
>  #endif
>  
> +/* virtio-pstore-pci */
> +
> +static void virtio_pstore_pci_realize(VirtIOPCIProxy *vpci_dev, Error
**errp)
> +{
> +    VirtIOPstorePCI *vps = VIRTIO_PSTORE_PCI(vpci_dev);
> +    DeviceState *vdev = DEVICE(&vps->vdev);
> +    Error *err = NULL;
> +
> +    qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
> +    object_property_set_bool(OBJECT(vdev), true, "realized",
&err);
> +    if (err) {
> +        error_propagate(errp, err);
> +        return;
> +    }
> +}
> +
> +static void virtio_pstore_pci_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass);
> +    PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass);
> +
> +    k->realize = virtio_pstore_pci_realize;
> +    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
> +
> +    pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
> +    pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_PSTORE;
> +    pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
> +    pcidev_k->class_id = PCI_CLASS_OTHERS;
> +}
> +
> +static void virtio_pstore_pci_instance_init(Object *obj)
> +{
> +    VirtIOPstorePCI *dev = VIRTIO_PSTORE_PCI(obj);
> +
> +    virtio_instance_init_common(obj, &dev->vdev,
sizeof(dev->vdev),
> +                                TYPE_VIRTIO_PSTORE);
> +    object_property_add_alias(obj, "directory",
OBJECT(&dev->vdev),
> +                              "directory", &error_abort);
> +    object_property_add_alias(obj, "bufsize",
OBJECT(&dev->vdev),
> +                              "bufsize", &error_abort);
> +    object_property_add_alias(obj, "console",
OBJECT(&dev->vdev),
> +                              "console", &error_abort);
> +}
> +
> +static const TypeInfo virtio_pstore_pci_info = {
> +    .name          = TYPE_VIRTIO_PSTORE_PCI,
> +    .parent        = TYPE_VIRTIO_PCI,
> +    .instance_size = sizeof(VirtIOPstorePCI),
> +    .instance_init = virtio_pstore_pci_instance_init,
> +    .class_init    = virtio_pstore_pci_class_init,
> +};
> +
>  /* virtio-pci-bus */
>  
>  static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
> @@ -2483,6 +2536,7 @@ static void virtio_pci_register_types(void)
>  #ifdef CONFIG_VHOST_SCSI
>      type_register_static(&vhost_scsi_pci_info);
>  #endif
> +    type_register_static(&virtio_pstore_pci_info);
>  }
>  
>  type_init(virtio_pci_register_types)
> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> index e4548c2..b4c039f 100644
> --- a/hw/virtio/virtio-pci.h
> +++ b/hw/virtio/virtio-pci.h
> @@ -31,6 +31,7 @@
>  #ifdef CONFIG_VHOST_SCSI
>  #include "hw/virtio/vhost-scsi.h"
>  #endif
> +#include "hw/virtio/virtio-pstore.h"
>  
>  typedef struct VirtIOPCIProxy VirtIOPCIProxy;
>  typedef struct VirtIOBlkPCI VirtIOBlkPCI;
> @@ -44,6 +45,7 @@ typedef struct VirtIOInputPCI VirtIOInputPCI;
>  typedef struct VirtIOInputHIDPCI VirtIOInputHIDPCI;
>  typedef struct VirtIOInputHostPCI VirtIOInputHostPCI;
>  typedef struct VirtIOGPUPCI VirtIOGPUPCI;
> +typedef struct VirtIOPstorePCI VirtIOPstorePCI;
>  
>  /* virtio-pci-bus */
>  
> @@ -311,6 +313,18 @@ struct VirtIOGPUPCI {
>      VirtIOGPU vdev;
>  };
>  
> +/*
> + * virtio-pstore-pci: This extends VirtioPCIProxy.
> + */
> +#define TYPE_VIRTIO_PSTORE_PCI "virtio-pstore-pci"
> +#define VIRTIO_PSTORE_PCI(obj) \
> +        OBJECT_CHECK(VirtIOPstorePCI, (obj), TYPE_VIRTIO_PSTORE_PCI)
> +
> +struct VirtIOPstorePCI {
> +    VirtIOPCIProxy parent_obj;
> +    VirtIOPstore vdev;
> +};
> +
>  /* Virtio ABI version, if we increment this, we break the guest driver. */
>  #define VIRTIO_PCI_ABI_VERSION          0
>  
> diff --git a/hw/virtio/virtio-pstore.c b/hw/virtio/virtio-pstore.c
> new file mode 100644
> index 0000000..2ca7786
> --- /dev/null
> +++ b/hw/virtio/virtio-pstore.c
> @@ -0,0 +1,477 @@
> +/*
> + * Virtio Pstore Device
> + *
> + * Copyright (C) 2016  LG Electronics
> + *
> + * Authors:
> + *  Namhyung Kim  <namhyung at gmail.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
We generally ask new code to be v2 or later.
>  See
> + * the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include <stdio.h>
> +
> +#include "qemu/osdep.h"
> +#include "qemu/iov.h"
> +#include "qemu-common.h"
> +#include "qemu/cutils.h"
> +#include "qemu/error-report.h"
> +#include "sysemu/kvm.h"
> +#include "qapi/visitor.h"
> +#include "qapi-event.h"
> +#include "trace.h"
> +
> +#include "hw/virtio/virtio.h"
> +#include "hw/virtio/virtio-bus.h"
> +#include "hw/virtio/virtio-access.h"
> +#include "hw/virtio/virtio-pstore.h"
> +
> +
> +static void virtio_pstore_to_filename(VirtIOPstore *s, char *buf, size_t
sz,
> +                                      struct virtio_pstore_req *req)
> +{
> +    const char *basename;
> +    unsigned long long id = 0;
> +    unsigned int flags = le32_to_cpu(req->flags);
> +
> +    switch (le16_to_cpu(req->type)) {
> +    case VIRTIO_PSTORE_TYPE_DMESG:
> +        basename = "dmesg";
> +        id = s->id++;
> +        break;
> +    case VIRTIO_PSTORE_TYPE_CONSOLE:
> +        basename = "console";
> +        if (s->console_id) {
> +            id = s->console_id;
> +        } else {
> +            id = s->console_id = s->id++;
> +        }
> +        break;
> +    default:
> +        basename = "unknown";
> +        break;
> +    }
> +
> +    snprintf(buf, sz, "%s/%s-%llu%s", s->directory, basename,
id,
> +             flags & VIRTIO_PSTORE_FL_COMPRESSED ? ".enc.z"
: "");
> +}
> +
> +static void virtio_pstore_from_filename(VirtIOPstore *s, char *name,
> +                                        char *buf, size_t sz,
> +                                        struct virtio_pstore_fileinfo
*info)
> +{
> +    snprintf(buf, sz, "%s/%s", s->directory, name);
if this does not fit, buf will not be 0 terminated and can
generally be corrupted.

> +
> +    if (g_str_has_prefix(name, "dmesg-")) {
> +        info->type = VIRTIO_PSTORE_TYPE_DMESG;
> +        name += strlen("dmesg-");
> +    } else if (g_str_has_prefix(name, "console-")) {
> +        info->type = VIRTIO_PSTORE_TYPE_CONSOLE;
> +        name += strlen("console-");
> +    } else if (g_str_has_prefix(name, "unknown-")) {
> +        info->type = VIRTIO_PSTORE_TYPE_UNKNOWN;
> +        name += strlen("unknown-");
> +    }
> +
> +    qemu_strtoull(name, NULL, 0, &info->id);
> +
> +    info->flags = 0;
> +    if (g_str_has_suffix(name, ".enc.z")) {
> +        info->flags |= VIRTIO_PSTORE_FL_COMPRESSED;
> +    }
> +}
> +
> +static ssize_t virtio_pstore_do_open(VirtIOPstore *s)
> +{
> +    s->dirp = opendir(s->directory);
> +    if (s->dirp == NULL) {
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +static ssize_t virtio_pstore_do_read(VirtIOPstore *s, struct iovec *in_sg,
> +                                     unsigned int in_num,
> +                                     struct virtio_pstore_res *res)
> +{
> +    char path[PATH_MAX];
> +    int fd;
> +    ssize_t len;
> +    struct stat stbuf;
> +    struct dirent *dent;
> +    int sg_num = in_num;
> +    struct iovec sg[sg_num];
> +    struct virtio_pstore_fileinfo info;
> +    size_t offset = sizeof(*res) + sizeof(info);
> +
> +    if (s->dirp == NULL) {
> +        return -1;
> +    }
> +
> +    dent = readdir(s->dirp);
> +    while (dent) {
> +        if (dent->d_name[0] != '.') {
> +            break;
> +        }
> +        dent = readdir(s->dirp);
> +    }
> +
> +    if (dent == NULL) {
> +        return 0;
> +    }
> +
> +    /* skip res and fileinfo */
> +    sg_num = iov_copy(sg, sg_num, in_sg, in_num, offset,
> +                      iov_size(in_sg, in_num) - offset);
> +
> +    virtio_pstore_from_filename(s, dent->d_name, path, sizeof(path),
&info);
> +    fd = open(path, O_RDONLY);
> +    if (fd < 0) {
> +        error_report("cannot open %s", path);
> +        return -1;
> +    }
> +
> +    if (fstat(fd, &stbuf) < 0) {
> +        len = -1;
> +        goto out;
> +    }
> +
> +    len = readv(fd, sg, sg_num);
> +    if (len < 0) {
> +        if (errno == EAGAIN) {
> +            len = 0;
> +        }
> +        goto out;
> +    }
> +
> +    info.id        = cpu_to_le64(info.id);
> +    info.type      = cpu_to_le16(info.type);
> +    info.flags     = cpu_to_le32(info.flags);
> +    info.len       = cpu_to_le32(len);
> +    info.time_sec  = cpu_to_le64(stbuf.st_ctim.tv_sec);
> +    info.time_nsec = cpu_to_le32(stbuf.st_ctim.tv_nsec);
> +
> +    iov_from_buf(in_sg, in_num, sizeof(*res), &info, sizeof(info));
> +    len += sizeof(info);
> +
> + out:
> +    close(fd);
> +    return len;
> +}
> +
> +static ssize_t virtio_pstore_do_write(VirtIOPstore *s, struct iovec
*out_sg,
> +                                      unsigned int out_num,
> +                                      struct virtio_pstore_req *req)
> +{
> +    char path[PATH_MAX];
> +    int fd;
> +    ssize_t len;
> +    unsigned short type;
> +    int flags = O_WRONLY | O_CREAT;
> +
> +    /* we already consume the req */
> +    iov_discard_front(&out_sg, &out_num, sizeof(*req));
> +
> +    virtio_pstore_to_filename(s, path, sizeof(path), req);
> +
> +    type = le16_to_cpu(req->type);
> +
> +    if (type == VIRTIO_PSTORE_TYPE_DMESG) {
> +        flags |= O_TRUNC;
> +    } else if (type == VIRTIO_PSTORE_TYPE_CONSOLE) {
> +        flags |= O_APPEND;
> +    }
> +
> +    fd = open(path, flags, 0644);
> +    if (fd < 0) {
> +        error_report("cannot open %s", path);
> +        return -1;
> +    }
> +    len = writev(fd, out_sg, out_num);
> +    close(fd);
> +
> +    return len;
All this is blocking VM until host io completes.

> +}
> +
> +static ssize_t virtio_pstore_do_close(VirtIOPstore *s)
> +{
> +    if (s->dirp == NULL) {
> +        return 0;
> +    }
> +
> +    closedir(s->dirp);
> +    s->dirp = NULL;
> +
> +    return 0;
> +}
> +
> +static ssize_t virtio_pstore_do_erase(VirtIOPstore *s,
> +                                      struct virtio_pstore_req *req)
> +{
> +    char path[PATH_MAX];
> +
> +    virtio_pstore_to_filename(s, path, sizeof(path), req);
> +
> +    return unlink(path);
> +}
> +
> +static void virtio_pstore_handle_io(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    VirtIOPstore *s = VIRTIO_PSTORE(vdev);
> +    VirtQueueElement *elem;
> +    struct virtio_pstore_req req;
> +    struct virtio_pstore_res res;
> +    ssize_t len = 0;
> +    int ret;
> +
> +    for (;;) {
> +        elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> +        if (!elem) {
> +            return;
> +        }
> +
> +        if (elem->out_num < 1 || elem->in_num < 1) {
> +            error_report("request or response buffer is
missing");
> +            exit(1);
> +        }
> +
> +        len = iov_to_buf(elem->out_sg, elem->out_num, 0, &req,
sizeof(req));
> +        if (len != (ssize_t)sizeof(req)) {
> +            error_report("invalid request size: %ld",
(long)len);
> +            exit(1);
> +        }
> +        res.cmd  = req.cmd;
> +        res.type = req.type;
> +
> +        switch (le16_to_cpu(req.cmd)) {
> +        case VIRTIO_PSTORE_CMD_OPEN:
> +            ret = virtio_pstore_do_open(s);
> +            break;
> +        case VIRTIO_PSTORE_CMD_READ:
> +            ret = virtio_pstore_do_read(s, elem->in_sg,
elem->in_num, &res);
> +            if (ret > 0) {
> +                len = ret;
> +                ret = 0;
> +            }
> +            break;
> +        case VIRTIO_PSTORE_CMD_WRITE:
> +            ret = virtio_pstore_do_write(s, elem->out_sg,
elem->out_num, &req);
> +            break;
> +        case VIRTIO_PSTORE_CMD_CLOSE:
> +            ret = virtio_pstore_do_close(s);
> +            break;
> +        case VIRTIO_PSTORE_CMD_ERASE:
> +            ret = virtio_pstore_do_erase(s, &req);
> +            break;
> +        default:
> +            ret = -1;
> +            break;
> +        }
> +
> +        res.ret  = ret;
> +
> +        iov_from_buf(elem->in_sg, elem->in_num, 0, &res,
sizeof(res));
> +        virtqueue_push(vq, elem, sizeof(res) + len);

this is wrong - len should be # of bytes written into guest memory.
> +
> +        virtio_notify(vdev, vq);
> +        g_free(elem);
> +
> +        if (ret < 0) {
> +            return;
> +        }
> +    }
> +}
> +
> +static void virtio_pstore_device_realize(DeviceState *dev, Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VirtIOPstore *s = VIRTIO_PSTORE(dev);
> +
> +    virtio_init(vdev, "virtio-pstore", VIRTIO_ID_PSTORE,
> +                sizeof(struct virtio_pstore_config));
> +
> +    s->id = 1;
> +    s->console_id = 0;
> +
> +    s->vq[0] = virtio_add_queue(vdev, 128, virtio_pstore_handle_io);
> +    s->vq[1] = virtio_add_queue(vdev, 128, virtio_pstore_handle_io);
> +}
> +
> +static void virtio_pstore_device_unrealize(DeviceState *dev, Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +
> +    virtio_cleanup(vdev);
> +}
> +
> +static void virtio_pstore_get_config(VirtIODevice *vdev, uint8_t
*config_data)
> +{
> +    VirtIOPstore *dev = VIRTIO_PSTORE(vdev);
> +    struct virtio_pstore_config config;
> +
> +    config.bufsize = cpu_to_le32(dev->bufsize);
> +    if (dev->console) {
> +        config.flags |= cpu_to_le32(VIRTIO_PSTORE_CONFIG_FL_CONSOLE);
> +    }
> +
> +    memcpy(config_data, &config, sizeof(struct virtio_pstore_config));
> +}
> +
> +static void virtio_pstore_set_config(VirtIODevice *vdev,
> +                                     const uint8_t *config_data)
> +{
> +    VirtIOPstore *dev = VIRTIO_PSTORE(vdev);
> +    struct virtio_pstore_config config;
> +
> +    memcpy(&config, config_data, sizeof(struct virtio_pstore_config));
> +
> +    dev->bufsize = le32_to_cpu(config.bufsize);
> +}
> +
> +static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
> +{
> +    return f;
> +}
> +
> +static void pstore_get_directory(Object *obj, Visitor *v,
> +                                 const char *name, void *opaque,
> +                                 Error **errp)
> +{
> +    VirtIOPstore *s = opaque;
> +
> +    visit_type_str(v, name, &s->directory, errp);
> +}
> +
> +static void pstore_set_directory(Object *obj, Visitor *v,
> +                                 const char *name, void *opaque,
> +                                 Error **errp)
> +{
> +    VirtIOPstore *s = opaque;
> +    Error *local_err = NULL;
> +    char *value;
> +
> +    visit_type_str(v, name, &value, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +
> +    g_free(s->directory);
> +    s->directory = value;
> +}
> +
> +static void pstore_release_directory(Object *obj, const char *name,
> +                                     void *opaque)
> +{
> +    VirtIOPstore *s = opaque;
> +
> +    g_free(s->directory);
> +    s->directory = NULL;
> +}
> +
> +static void pstore_get_bufsize(Object *obj, Visitor *v,
> +                               const char *name, void *opaque,
> +                               Error **errp)
> +{
> +    VirtIOPstore *s = opaque;
> +    uint64_t value = s->bufsize;
> +
> +    visit_type_size(v, name, &value, errp);
> +}
> +
> +static void pstore_set_bufsize(Object *obj, Visitor *v,
> +                               const char *name, void *opaque,
> +                               Error **errp)
> +{
> +    VirtIOPstore *s = opaque;
> +    Error *error = NULL;
> +    uint64_t value;
> +
> +    visit_type_size(v, name, &value, &error);
> +    if (error) {
> +        error_propagate(errp, error);
> +        return;
> +    }
> +
> +    if (value < 4096) {
> +        error_report("Warning: too small buffer size: %"PRIu64,
value);
> +    }
> +
> +    s->bufsize = value;
> +}
> +
> +static void pstore_get_console(Object *obj, Visitor *v,
> +                               const char *name, void *opaque,
> +                               Error **errp)
> +{
> +    VirtIOPstore *s = opaque;
> +    bool value = s->console;
> +
> +    visit_type_bool(v, name, &value, errp);
> +}
> +
> +static void pstore_set_console(Object *obj, Visitor *v,
> +                               const char *name, void *opaque,
> +                               Error **errp)
> +{
> +    VirtIOPstore *s = opaque;
> +    Error *error = NULL;
> +    bool value;
> +
> +    visit_type_bool(v, name, &value, &error);
> +    if (error) {
> +        error_propagate(errp, error);
> +        return;
> +    }
> +
> +    s->console = value;
> +}
> +
> +static Property virtio_pstore_properties[] = {
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void virtio_pstore_instance_init(Object *obj)
> +{
> +    VirtIOPstore *s = VIRTIO_PSTORE(obj);
> +
> +    object_property_add(obj, "directory", "str",
> +                        pstore_get_directory, pstore_set_directory,
> +                        pstore_release_directory, s, NULL);
> +    object_property_add(obj, "bufsize", "size",
> +                        pstore_get_bufsize, pstore_set_bufsize, NULL, s,
NULL);
> +    object_property_add(obj, "console", "bool",
> +                        pstore_get_console, pstore_set_console, NULL, s,
NULL);
> +}
> +
> +static void virtio_pstore_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
> +
> +    dc->props = virtio_pstore_properties;
> +    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
> +    vdc->realize = virtio_pstore_device_realize;
> +    vdc->unrealize = virtio_pstore_device_unrealize;
> +    vdc->get_config = virtio_pstore_get_config;
> +    vdc->set_config = virtio_pstore_set_config;
> +    vdc->get_features = get_features;
> +}
> +
> +static const TypeInfo virtio_pstore_info = {
> +    .name = TYPE_VIRTIO_PSTORE,
> +    .parent = TYPE_VIRTIO_DEVICE,
> +    .instance_size = sizeof(VirtIOPstore),
> +    .instance_init = virtio_pstore_instance_init,
> +    .class_init = virtio_pstore_class_init,
> +};
> +
> +static void virtio_register_types(void)
> +{
> +    type_register_static(&virtio_pstore_info);
> +}
> +
> +type_init(virtio_register_types)
> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> index 74d797d..000e1e9 100644
> --- a/include/hw/pci/pci.h
> +++ b/include/hw/pci/pci.h
> @@ -79,6 +79,7 @@
>  #define PCI_DEVICE_ID_VIRTIO_SCSI        0x1004
>  #define PCI_DEVICE_ID_VIRTIO_RNG         0x1005
>  #define PCI_DEVICE_ID_VIRTIO_9P          0x1009
> +#define PCI_DEVICE_ID_VIRTIO_PSTORE      0x100a
>  
>  #define PCI_VENDOR_ID_REDHAT             0x1b36
>  #define PCI_DEVICE_ID_REDHAT_BRIDGE      0x0001
> diff --git a/include/hw/virtio/virtio-pstore.h
b/include/hw/virtio/virtio-pstore.h
> new file mode 100644
> index 0000000..d188a48
> --- /dev/null
> +++ b/include/hw/virtio/virtio-pstore.h
> @@ -0,0 +1,34 @@
> +/*
> + * Virtio Pstore Support
> + *
> + * Authors:
> + *  Namhyung Kim      <namhyung at gmail.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef _QEMU_VIRTIO_PSTORE_H
> +#define _QEMU_VIRTIO_PSTORE_H
> +
> +#include "standard-headers/linux/virtio_pstore.h"
> +#include "hw/virtio/virtio.h"
> +#include "hw/pci/pci.h"
> +
> +#define TYPE_VIRTIO_PSTORE "virtio-pstore-device"
> +#define VIRTIO_PSTORE(obj) \
> +        OBJECT_CHECK(VirtIOPstore, (obj), TYPE_VIRTIO_PSTORE)
> +
> +typedef struct VirtIOPstore {
> +    VirtIODevice    parent_obj;
> +    VirtQueue      *vq[2];
> +    char           *directory;
> +    uint64_t        id;
> +    uint64_t        console_id;
> +    DIR            *dirp;
> +    uint64_t        bufsize;
> +    bool            console;
> +} VirtIOPstore;
> +
> +#endif
> diff --git a/include/standard-headers/linux/virtio_ids.h
b/include/standard-headers/linux/virtio_ids.h
> index 77925f5..c72a9ab 100644
> --- a/include/standard-headers/linux/virtio_ids.h
> +++ b/include/standard-headers/linux/virtio_ids.h
> @@ -41,5 +41,6 @@
>  #define VIRTIO_ID_CAIF	       12 /* Virtio caif */
>  #define VIRTIO_ID_GPU          16 /* virtio GPU */
>  #define VIRTIO_ID_INPUT        18 /* virtio input */
> +#define VIRTIO_ID_PSTORE       22 /* virtio pstore */
>  
>  #endif /* _LINUX_VIRTIO_IDS_H */
> diff --git a/include/standard-headers/linux/virtio_pstore.h
b/include/standard-headers/linux/virtio_pstore.h
> new file mode 100644
> index 0000000..b893d15
> --- /dev/null
> +++ b/include/standard-headers/linux/virtio_pstore.h
> @@ -0,0 +1,80 @@
> +#ifndef _LINUX_VIRTIO_PSTORE_H
> +#define _LINUX_VIRTIO_PSTORE_H
> +/* This header is BSD licensed so anyone can use the definitions to
implement
> + * compatible drivers/servers.
> + *
> + * Redistribution and use in source and binary forms, with or without
> + * modification, are permitted provided that the following conditions
> + * are met:
> + * 1. Redistributions of source code must retain the above copyright
> + *    notice, this list of conditions and the following disclaimer.
> + * 2. Redistributions in binary form must reproduce the above copyright
> + *    notice, this list of conditions and the following disclaimer in the
> + *    documentation and/or other materials provided with the distribution.
> + * 3. Neither the name of IBM nor the names of its contributors
> + *    may be used to endorse or promote products derived from this
software
> + *    without specific prior written permission.
> + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
``AS IS'' AND
> + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
> + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE
> + * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
> + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL
> + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
> + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
> + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT
> + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
WAY
> + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> + * SUCH DAMAGE. */
> +#include "standard-headers/linux/types.h"
> +#include "standard-headers/linux/virtio_types.h"
> +#include "standard-headers/linux/virtio_ids.h"
> +#include "standard-headers/linux/virtio_config.h"
> +
> +#define VIRTIO_PSTORE_CMD_NULL   0
> +#define VIRTIO_PSTORE_CMD_OPEN   1
> +#define VIRTIO_PSTORE_CMD_READ   2
> +#define VIRTIO_PSTORE_CMD_WRITE  3
> +#define VIRTIO_PSTORE_CMD_ERASE  4
> +#define VIRTIO_PSTORE_CMD_CLOSE  5
> +
> +#define VIRTIO_PSTORE_TYPE_UNKNOWN  0
> +#define VIRTIO_PSTORE_TYPE_DMESG    1
> +#define VIRTIO_PSTORE_TYPE_CONSOLE  2
> +
> +#define VIRTIO_PSTORE_FL_COMPRESSED  1
> +
> +#define VIRTIO_PSTORE_CONFIG_FL_CONSOLE  (1 << 0)
> +
> +struct virtio_pstore_req {
> +    __virtio16 cmd;
> +    __virtio16 type;
> +    __virtio32 flags;
> +    __virtio64 id;
> +    __virtio32 count;
> +    __virtio32 reserved;
> +};
> +
> +struct virtio_pstore_res {
> +    __virtio16 cmd;
> +    __virtio16 type;
> +    __virtio32 ret;
> +};
> +
> +struct virtio_pstore_fileinfo {
> +    __virtio64 id;
> +    __virtio32 count;
> +    __virtio16 type;
> +    __virtio16 unused;
> +    __virtio32 flags;
> +    __virtio32 len;
> +    __virtio64 time_sec;
> +    __virtio32 time_nsec;
> +    __virtio32 reserved;
> +};
> +
> +struct virtio_pstore_config {
> +    __virtio32 bufsize;
> +    __virtio32 flags;
> +};
> +
> +#endif /* _LINUX_VIRTIO_PSTORE_H */
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index e19617f..e1df5a9 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -73,6 +73,7 @@ static const QDevAlias qdev_alias_table[] = {
>      { "virtio-serial-pci", "virtio-serial",
QEMU_ARCH_ALL & ~QEMU_ARCH_S390X },
>      { "virtio-tablet-ccw", "virtio-tablet",
QEMU_ARCH_S390X },
>      { "virtio-tablet-pci", "virtio-tablet",
QEMU_ARCH_ALL & ~QEMU_ARCH_S390X },
> +    { "virtio-pstore-pci", "virtio-pstore" },
>      { }
>  };
>  
> -- 
> 2.8.0

Hello,

On Thu, Jul 28, 2016 at 01:18:42AM +0300, Michael S. Tsirkin
wrote:
> On Thu, Jul 28, 2016 at 12:08:24AM +0900, Namhyung Kim wrote:
> > Hello,
> > 
> > This is v2 of the virtio-pstore work.  In this patchset I addressed
> > most of feedbacks from previous version.  Limiting disk size is not
> > implemented yet.
> 
> For some reason, only parts of the patchset were received.
> Pls post all patches to all lists.
> 
> If you are changing the virtio interface with host,
> like a new device, they you must copy the virtio TC
> so make sure there are no objections from there.
> 
> https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio#feedback
Hmm.. I think I've CC-ed all the kvm, qemu and virtualization lists
but missed the virtio list, sorry.  Will add next time.

Thanks,
Namhyung

On Thu, Jul 28, 2016 at 12:08:30AM +0900, Namhyung Kim
wrote:
> Add virtio pstore device to allow kernel log files saved on the host.
> It will save the log files on the directory given by pstore device
> option.
> 
>   $ qemu-system-x86_64 -device virtio-pstore,directory=dir-xx ...
> 
>   (guest) # echo c > /proc/sysrq-trigger
> 
>   $ ls dir-xx
>   dmesg-1.enc.z  dmesg-2.enc.z
> 
> The log files are usually compressed using zlib.  Users can see the log
> messages directly on the host or on the guest (using pstore filesystem).
> 
> The 'directory' property is required for virtio-pstore device to
work.
> It also adds 'bufsize' and 'console' (boolean) properties.
> 
> Cc: Paolo Bonzini <pbonzini at redhat.com>
> Cc: Radim Kr?m?? <rkrcmar at redhat.com>
> Cc: "Michael S. Tsirkin" <mst at redhat.com>
> Cc: Anthony Liguori <aliguori at amazon.com>
> Cc: Anton Vorontsov <anton at enomsg.org>
> Cc: Colin Cross <ccross at android.com>
> Cc: Kees Cook <keescook at chromium.org>
> Cc: Tony Luck <tony.luck at intel.com>
> Cc: Steven Rostedt <rostedt at goodmis.org>
> Cc: Ingo Molnar <mingo at kernel.org>
> Cc: Minchan Kim <minchan at kernel.org>
> Cc: kvm at vger.kernel.org
> Cc: qemu-devel at nongnu.org
> Cc: virtualization at lists.linux-foundation.org
> Signed-off-by: Namhyung Kim <namhyung at kernel.org>
> ---
>  hw/virtio/Makefile.objs                        |   2 +-
>  hw/virtio/virtio-pci.c                         |  54 +++
>  hw/virtio/virtio-pci.h                         |  14 +
>  hw/virtio/virtio-pstore.c                      | 477
+++++++++++++++++++++++++
>  include/hw/pci/pci.h                           |   1 +
>  include/hw/virtio/virtio-pstore.h              |  34 ++
>  include/standard-headers/linux/virtio_ids.h    |   1 +
>  include/standard-headers/linux/virtio_pstore.h |  80 +++++
>  qdev-monitor.c                                 |   1 +
>  9 files changed, 663 insertions(+), 1 deletion(-)
>  create mode 100644 hw/virtio/virtio-pstore.c
>  create mode 100644 include/hw/virtio/virtio-pstore.h
>  create mode 100644 include/standard-headers/linux/virtio_pstore.h
> 
> diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
> index 3e2b175..aae7082 100644
> --- a/hw/virtio/Makefile.objs
> +++ b/hw/virtio/Makefile.objs
> @@ -4,4 +4,4 @@ common-obj-y += virtio-bus.o
>  common-obj-y += virtio-mmio.o
>  
>  obj-y += virtio.o virtio-balloon.o 
> -obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
> +obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
virtio-pstore.o
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index f0677b7..d99a405 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -2414,6 +2414,59 @@ static const TypeInfo virtio_host_pci_info = {
>  };
>  #endif
>  
> +/* virtio-pstore-pci */
> +
> +static void virtio_pstore_pci_realize(VirtIOPCIProxy *vpci_dev, Error
**errp)
> +{
> +    VirtIOPstorePCI *vps = VIRTIO_PSTORE_PCI(vpci_dev);
> +    DeviceState *vdev = DEVICE(&vps->vdev);
> +    Error *err = NULL;
> +
> +    qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
> +    object_property_set_bool(OBJECT(vdev), true, "realized",
&err);
> +    if (err) {
> +        error_propagate(errp, err);
> +        return;
> +    }
> +}
> +
> +static void virtio_pstore_pci_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass);
> +    PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass);
> +
> +    k->realize = virtio_pstore_pci_realize;
> +    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
> +
> +    pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
> +    pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_PSTORE;
> +    pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
> +    pcidev_k->class_id = PCI_CLASS_OTHERS;
> +}
> +
> +static void virtio_pstore_pci_instance_init(Object *obj)
> +{
> +    VirtIOPstorePCI *dev = VIRTIO_PSTORE_PCI(obj);
> +
> +    virtio_instance_init_common(obj, &dev->vdev,
sizeof(dev->vdev),
> +                                TYPE_VIRTIO_PSTORE);
> +    object_property_add_alias(obj, "directory",
OBJECT(&dev->vdev),
> +                              "directory", &error_abort);
> +    object_property_add_alias(obj, "bufsize",
OBJECT(&dev->vdev),
> +                              "bufsize", &error_abort);
> +    object_property_add_alias(obj, "console",
OBJECT(&dev->vdev),
> +                              "console", &error_abort);
> +}
> +
> +static const TypeInfo virtio_pstore_pci_info = {
> +    .name          = TYPE_VIRTIO_PSTORE_PCI,
> +    .parent        = TYPE_VIRTIO_PCI,
> +    .instance_size = sizeof(VirtIOPstorePCI),
> +    .instance_init = virtio_pstore_pci_instance_init,
> +    .class_init    = virtio_pstore_pci_class_init,
> +};
> +
>  /* virtio-pci-bus */
>  
>  static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
> @@ -2483,6 +2536,7 @@ static void virtio_pci_register_types(void)
>  #ifdef CONFIG_VHOST_SCSI
>      type_register_static(&vhost_scsi_pci_info);
>  #endif
> +    type_register_static(&virtio_pstore_pci_info);
>  }
>  
>  type_init(virtio_pci_register_types)
> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> index e4548c2..b4c039f 100644
> --- a/hw/virtio/virtio-pci.h
> +++ b/hw/virtio/virtio-pci.h
> @@ -31,6 +31,7 @@
>  #ifdef CONFIG_VHOST_SCSI
>  #include "hw/virtio/vhost-scsi.h"
>  #endif
> +#include "hw/virtio/virtio-pstore.h"
>  
>  typedef struct VirtIOPCIProxy VirtIOPCIProxy;
>  typedef struct VirtIOBlkPCI VirtIOBlkPCI;
> @@ -44,6 +45,7 @@ typedef struct VirtIOInputPCI VirtIOInputPCI;
>  typedef struct VirtIOInputHIDPCI VirtIOInputHIDPCI;
>  typedef struct VirtIOInputHostPCI VirtIOInputHostPCI;
>  typedef struct VirtIOGPUPCI VirtIOGPUPCI;
> +typedef struct VirtIOPstorePCI VirtIOPstorePCI;
>  
>  /* virtio-pci-bus */
>  
> @@ -311,6 +313,18 @@ struct VirtIOGPUPCI {
>      VirtIOGPU vdev;
>  };
>  
> +/*
> + * virtio-pstore-pci: This extends VirtioPCIProxy.
> + */
> +#define TYPE_VIRTIO_PSTORE_PCI "virtio-pstore-pci"
> +#define VIRTIO_PSTORE_PCI(obj) \
> +        OBJECT_CHECK(VirtIOPstorePCI, (obj), TYPE_VIRTIO_PSTORE_PCI)
> +
> +struct VirtIOPstorePCI {
> +    VirtIOPCIProxy parent_obj;
> +    VirtIOPstore vdev;
> +};
> +
>  /* Virtio ABI version, if we increment this, we break the guest driver. */
>  #define VIRTIO_PCI_ABI_VERSION          0
>  
> diff --git a/hw/virtio/virtio-pstore.c b/hw/virtio/virtio-pstore.c
> new file mode 100644
> index 0000000..2ca7786
> --- /dev/null
> +++ b/hw/virtio/virtio-pstore.c
> @@ -0,0 +1,477 @@
> +/*
> + * Virtio Pstore Device
> + *
> + * Copyright (C) 2016  LG Electronics
> + *
> + * Authors:
> + *  Namhyung Kim  <namhyung at gmail.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include <stdio.h>
> +
> +#include "qemu/osdep.h"
> +#include "qemu/iov.h"
> +#include "qemu-common.h"
> +#include "qemu/cutils.h"
> +#include "qemu/error-report.h"
> +#include "sysemu/kvm.h"
> +#include "qapi/visitor.h"
> +#include "qapi-event.h"
> +#include "trace.h"
> +
> +#include "hw/virtio/virtio.h"
> +#include "hw/virtio/virtio-bus.h"
> +#include "hw/virtio/virtio-access.h"
> +#include "hw/virtio/virtio-pstore.h"
> +
> +
> +static void virtio_pstore_to_filename(VirtIOPstore *s, char *buf, size_t
sz,
> +                                      struct virtio_pstore_req *req)
> +{
> +    const char *basename;
> +    unsigned long long id = 0;
> +    unsigned int flags = le32_to_cpu(req->flags);
> +
> +    switch (le16_to_cpu(req->type)) {
> +    case VIRTIO_PSTORE_TYPE_DMESG:
> +        basename = "dmesg";
> +        id = s->id++;
> +        break;
> +    case VIRTIO_PSTORE_TYPE_CONSOLE:
> +        basename = "console";
> +        if (s->console_id) {
> +            id = s->console_id;
> +        } else {
> +            id = s->console_id = s->id++;
> +        }
> +        break;
> +    default:
> +        basename = "unknown";
> +        break;
> +    }
> +
> +    snprintf(buf, sz, "%s/%s-%llu%s", s->directory, basename,
id,
> +             flags & VIRTIO_PSTORE_FL_COMPRESSED ? ".enc.z"
: "");
Please use g_strdup_printf() instead of splattering into a pre-allocated
buffer than may or may not be large enough.
> +}
> +
> +static void virtio_pstore_from_filename(VirtIOPstore *s, char *name,
> +                                        char *buf, size_t sz,
> +                                        struct virtio_pstore_fileinfo
*info)
> +{
> +    snprintf(buf, sz, "%s/%s", s->directory, name);
> +
> +    if (g_str_has_prefix(name, "dmesg-")) {
> +        info->type = VIRTIO_PSTORE_TYPE_DMESG;
> +        name += strlen("dmesg-");
> +    } else if (g_str_has_prefix(name, "console-")) {
> +        info->type = VIRTIO_PSTORE_TYPE_CONSOLE;
> +        name += strlen("console-");
> +    } else if (g_str_has_prefix(name, "unknown-")) {
> +        info->type = VIRTIO_PSTORE_TYPE_UNKNOWN;
> +        name += strlen("unknown-");
> +    }
> +
> +    qemu_strtoull(name, NULL, 0, &info->id);
> +
> +    info->flags = 0;
> +    if (g_str_has_suffix(name, ".enc.z")) {
> +        info->flags |= VIRTIO_PSTORE_FL_COMPRESSED;
> +    }
> +}
> +
> +static ssize_t virtio_pstore_do_open(VirtIOPstore *s)
> +{
> +    s->dirp = opendir(s->directory);
> +    if (s->dirp == NULL) {
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +static ssize_t virtio_pstore_do_read(VirtIOPstore *s, struct iovec *in_sg,
> +                                     unsigned int in_num,
> +                                     struct virtio_pstore_res *res)
> +{
> +    char path[PATH_MAX];
Don't declare PATH_MAX sized variables
> +    int fd;
> +    ssize_t len;
> +    struct stat stbuf;
> +    struct dirent *dent;
> +    int sg_num = in_num;
> +    struct iovec sg[sg_num];
'sg_num' is initialized from 'in_num' which comes from the
guest, and I'm not seeing anything which is bounds-checking
the 'in_num' value. So you've possibly got a security flaw here
I think, if the guest can cause QEMU to allocate arbitrary stack
memory & thus overflow by setting arbitrarily large in_num.
> +    struct virtio_pstore_fileinfo info;
> +    size_t offset = sizeof(*res) + sizeof(info);
> +
> +    if (s->dirp == NULL) {
> +        return -1;
> +    }
> +
> +    dent = readdir(s->dirp);
> +    while (dent) {
> +        if (dent->d_name[0] != '.') {
> +            break;
> +        }
> +        dent = readdir(s->dirp);
> +    }
> +
> +    if (dent == NULL) {
> +        return 0;
> +    }
So this seems to just be picking the first filename reported by
readdir that isn't starting with '.'. Surely this can't the
right
logic when your corresponding do_write method can pick several
different filenames, its potluck which do_read will give back.
> +
> +    /* skip res and fileinfo */
> +    sg_num = iov_copy(sg, sg_num, in_sg, in_num, offset,
> +                      iov_size(in_sg, in_num) - offset);
> +
> +    virtio_pstore_from_filename(s, dent->d_name, path, sizeof(path),
&info);
> +    fd = open(path, O_RDONLY);
> +    if (fd < 0) {
> +        error_report("cannot open %s", path);
> +        return -1;
> +    }
> +
> +    if (fstat(fd, &stbuf) < 0) {
> +        len = -1;
> +        goto out;
> +    }
> +
> +    len = readv(fd, sg, sg_num);
> +    if (len < 0) {
> +        if (errno == EAGAIN) {
> +            len = 0;
> +        }
> +        goto out;
> +    }
> +
> +    info.id        = cpu_to_le64(info.id);
> +    info.type      = cpu_to_le16(info.type);
> +    info.flags     = cpu_to_le32(info.flags);
> +    info.len       = cpu_to_le32(len);
> +    info.time_sec  = cpu_to_le64(stbuf.st_ctim.tv_sec);
> +    info.time_nsec = cpu_to_le32(stbuf.st_ctim.tv_nsec);
> +
> +    iov_from_buf(in_sg, in_num, sizeof(*res), &info, sizeof(info));
> +    len += sizeof(info);
> +
> + out:
> +    close(fd);
> +    return len;
> +}
> +
> +static ssize_t virtio_pstore_do_write(VirtIOPstore *s, struct iovec
*out_sg,
> +                                      unsigned int out_num,
> +                                      struct virtio_pstore_req *req)
> +{
> +    char path[PATH_MAX];
> +    int fd;
> +    ssize_t len;
> +    unsigned short type;
> +    int flags = O_WRONLY | O_CREAT;
> +
> +    /* we already consume the req */
> +    iov_discard_front(&out_sg, &out_num, sizeof(*req));
> +
> +    virtio_pstore_to_filename(s, path, sizeof(path), req);
> +
> +    type = le16_to_cpu(req->type);
> +
> +    if (type == VIRTIO_PSTORE_TYPE_DMESG) {
> +        flags |= O_TRUNC;
> +    } else if (type == VIRTIO_PSTORE_TYPE_CONSOLE) {
> +        flags |= O_APPEND;
Using O_APPEND will cause the file to grow without bound on the
host, which is highly undesirable, aka a security flaw.
> +    }
> +
> +    fd = open(path, flags, 0644);
> +    if (fd < 0) {
> +        error_report("cannot open %s", path);
> +        return -1;
> +    }
> +    len = writev(fd, out_sg, out_num);
> +    close(fd);
> +
> +    return len;
> +}

Regards,
Daniel
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