Linux Virtualization - Jan 2010 - [PATCH 00/32] virtio: console: Fixes, multiple devices and generic ports

Hey Rusty,

In this version:
- Assume only one inbuf; no input buffering for ports
- Remove the START/END delimiters for outgoing buffers
- Remove the header that was sent along with each buffer
- Remove unused buffers in the vqs at port remove time
- Send a guest port open message to the host when a console port is
  attached
- Remove cached buffers when ports are closed / disconnected
- Send only one buffer in send_buf

As usual, this series is passed through the testsuite that tests for
the functionality given here.

Amit Shah (25):
  hvc_console: Remove __devinit annotation from hvc_alloc
  virtio: console: We support only one device at a time
  virtio: console: encapsulate buffer information in a struct
  virtio: console: ensure add_inbuf can work for multiple ports as well
  virtio: console: introduce a get_inbuf helper to fetch bufs from
    in_vq
  virtio: console: don't assume a single console port.
  virtio: console: struct ports for multiple ports per device.
  virtio: console: ensure console size is updated on hvc open
  virtio: console: Separate out console-specific data into a separate
    struct
  virtio: console: Separate out console init into a new function
  virtio: console: Separate out find_vqs operation into a different
    function
  virtio: console: Introduce function to hand off data from host to
    readers
  virtio: console: Introduce a send_buf function for a common path for
    sending data to host
  virtio: console: Add a new MULTIPORT feature, support for generic
    ports
  virtio: console: Prepare for writing to / reading from userspace
    buffers
  virtio: console: Associate each port with a char device
  virtio: console: Add file operations to ports for
    open/read/write/poll
  virtio: console: Ensure only one process can have a port open at a
    time
  virtio: console: Register with sysfs and create a 'name' attribute
    for ports
  virtio: console: Add throttling support to prevent flooding ports
  virtio: console: Remove cached data on port close
  virtio: console: Handle port hot-plug
  virtio: console: Add ability to hot-unplug ports
  virtio: console: Add debugfs files for each port to expose debug info
  virtio: console: show error message if hvc_alloc fails for console
    ports

Rusty Russell (6):
  virtio: console: comment cleanup
  virtio: console: statically initialize virtio_cons
  hvc_console: make the ops pointer const.
  virtio: console: port encapsulation
  virtio: console: use vdev->priv to avoid accessing global var.
  virtio: console: remove global var

Shirley Ma (1):
  virtio: Add ability to detach unused buffers from vrings

 drivers/char/Kconfig           |    8 +
 drivers/char/hvc_beat.c        |    2 +-
 drivers/char/hvc_console.c     |    9 +-
 drivers/char/hvc_console.h     |    9 +-
 drivers/char/hvc_iseries.c     |    2 +-
 drivers/char/hvc_iucv.c        |    2 +-
 drivers/char/hvc_rtas.c        |    2 +-
 drivers/char/hvc_udbg.c        |    2 +-
 drivers/char/hvc_vio.c         |    2 +-
 drivers/char/hvc_xen.c         |    2 +-
 drivers/char/virtio_console.c  | 1559 ++++++++++++++++++++++++++++++++++++----
 drivers/virtio/virtio_ring.c   |   25 +
 include/linux/virtio.h         |    4 +
 include/linux/virtio_console.h |   31 +-
 14 files changed, 1496 insertions(+), 163 deletions(-)

From: Rusty Russell <rusty at rustcorp.com.au>

Remove old lguest-style comments.

[Amit: - wingify comments acc. to kernel style
       - indent comments ]

Signed-off-by: Rusty Russell <rusty at rustcorp.com.au>
Signed-off-by: Amit Shah <amit.shah at redhat.com>
---
 drivers/char/virtio_console.c  |  108 ++++++++++++++++++++--------------------
 include/linux/virtio_console.h |    6 ++-
 2 files changed, 58 insertions(+), 56 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index a035ae3..26e238c 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1,18 +1,5 @@
-/*D:300
- * The Guest console driver
- *
- * Writing console drivers is one of the few remaining Dark Arts in Linux.
- * Fortunately for us, the path of virtual consoles has been well-trodden by
- * the PowerPC folks, who wrote "hvc_console.c" to generically
support any
- * virtual console.  We use that infrastructure which only requires us to write
- * the basic put_chars and get_chars functions and call the right register
- * functions.
- :*/
-
-/*M:002 The console can be flooded: while the Guest is processing input the
- * Host can send more.  Buffering in the Host could alleviate this, but it is a
- * difficult problem in general. :*/
-/* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
+/*
+ * Copyright (C) 2006, 2007, 2009 Rusty Russell, IBM Corporation
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -34,8 +21,6 @@
 #include <linux/virtio_console.h>
 #include "hvc_console.h"
 
-/*D:340 These represent our input and output console queues, and the virtio
- * operations for them. */
 static struct virtqueue *in_vq, *out_vq;
 static struct virtio_device *vdev;
 
@@ -49,12 +34,14 @@ static struct hv_ops virtio_cons;
 /* The hvc device */
 static struct hvc_struct *hvc;
 
-/*D:310 The put_chars() callback is pretty straightforward.
+/*
+ * The put_chars() callback is pretty straightforward.
  *
- * We turn the characters into a scatter-gather list, add it to the output
- * queue and then kick the Host.  Then we sit here waiting for it to finish:
- * inefficient in theory, but in practice implementations will do it
- * immediately (lguest's Launcher does). */
+ * We turn the characters into a scatter-gather list, add it to the
+ * output queue and then kick the Host.  Then we sit here waiting for
+ * it to finish: inefficient in theory, but in practice
+ * implementations will do it immediately (lguest's Launcher does).
+ */
 static int put_chars(u32 vtermno, const char *buf, int count)
 {
 	struct scatterlist sg[1];
@@ -63,8 +50,10 @@ static int put_chars(u32 vtermno, const char *buf, int count)
 	/* This is a convenient routine to initialize a single-elem sg list */
 	sg_init_one(sg, buf, count);
 
-	/* add_buf wants a token to identify this buffer: we hand it any
-	 * non-NULL pointer, since there's only ever one buffer. */
+	/*
+	 * add_buf wants a token to identify this buffer: we hand it
+	 * any non-NULL pointer, since there's only ever one buffer.
+	 */
 	if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) >= 0) {
 		/* Tell Host to go! */
 		out_vq->vq_ops->kick(out_vq);
@@ -77,8 +66,10 @@ static int put_chars(u32 vtermno, const char *buf, int count)
 	return count;
 }
 
-/* Create a scatter-gather list representing our input buffer and put it in the
- * queue. */
+/*
+ * Create a scatter-gather list representing our input buffer and put
+ * it in the queue.
+ */
 static void add_inbuf(void)
 {
 	struct scatterlist sg[1];
@@ -90,12 +81,14 @@ static void add_inbuf(void)
 	in_vq->vq_ops->kick(in_vq);
 }
 
-/*D:350 get_chars() is the callback from the hvc_console infrastructure when
- * an interrupt is received.
+/*
+ * get_chars() is the callback from the hvc_console infrastructure
+ * when an interrupt is received.
  *
- * Most of the code deals with the fact that the hvc_console() infrastructure
- * only asks us for 16 bytes at a time.  We keep in_offset and in_used fields
- * for partially-filled buffers. */
+ * Most of the code deals with the fact that the hvc_console()
+ * infrastructure only asks us for 16 bytes at a time.  We keep
+ * in_offset and in_used fields for partially-filled buffers.
+ */
 static int get_chars(u32 vtermno, char *buf, int count)
 {
 	/* If we don't have an input queue yet, we can't get input. */
@@ -123,14 +116,16 @@ static int get_chars(u32 vtermno, char *buf, int count)
 
 	return count;
 }
-/*:*/
 
-/*D:320 Console drivers are initialized very early so boot messages can go out,
- * so we do things slightly differently from the generic virtio initialization
- * of the net and block drivers.
+/*
+ * Console drivers are initialized very early so boot messages can go
+ * out, so we do things slightly differently from the generic virtio
+ * initialization of the net and block drivers.
  *
- * At this stage, the console is output-only.  It's too early to set up a
- * virtqueue, so we let the drivers do some boutique early-output thing. */
+ * At this stage, the console is output-only.  It's too early to set
+ * up a virtqueue, so we let the drivers do some boutique early-output
+ * thing.
+ */
 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
 {
 	virtio_cons.put_chars = put_chars;
@@ -157,8 +152,8 @@ static void virtcons_apply_config(struct virtio_device *dev)
 }
 
 /*
- * we support only one console, the hvc struct is a global var
- * We set the configuration at this point, since we now have a tty
+ * we support only one console, the hvc struct is a global var We set
+ * the configuration at this point, since we now have a tty
  */
 static int notifier_add_vio(struct hvc_struct *hp, int data)
 {
@@ -179,13 +174,17 @@ static void hvc_handle_input(struct virtqueue *vq)
 		hvc_kick();
 }
 
-/*D:370 Once we're further in boot, we get probed like any other virtio
device.
- * At this stage we set up the output virtqueue.
+/*
+ * Once we're further in boot, we get probed like any other virtio
+ * device.  At this stage we set up the output virtqueue.
  *
- * To set up and manage our virtual console, we call hvc_alloc().  Since we
- * never remove the console device we never need this pointer again.
+ * To set up and manage our virtual console, we call hvc_alloc().
+ * Since we never remove the console device we never need this pointer
+ * again.
  *
- * Finally we put our input buffer in the input queue, ready to receive. */
+ * Finally we put our input buffer in the input queue, ready to
+ * receive.
+ */
 static int __devinit virtcons_probe(struct virtio_device *dev)
 {
 	vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
@@ -203,8 +202,6 @@ static int __devinit virtcons_probe(struct virtio_device
*dev)
 	}
 
 	/* Find the queues. */
-	/* FIXME: This is why we want to wean off hvc: we do nothing
-	 * when input comes in. */
 	err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
 	if (err)
 		goto free;
@@ -219,15 +216,18 @@ static int __devinit virtcons_probe(struct virtio_device
*dev)
 	virtio_cons.notifier_del = notifier_del_vio;
 	virtio_cons.notifier_hangup = notifier_del_vio;
 
-	/* The first argument of hvc_alloc() is the virtual console number, so
-	 * we use zero.  The second argument is the parameter for the
-	 * notification mechanism (like irq number). We currently leave this
-	 * as zero, virtqueues have implicit notifications.
+	/*
+	 * The first argument of hvc_alloc() is the virtual console
+	 * number, so we use zero.  The second argument is the
+	 * parameter for the notification mechanism (like irq
+	 * number). We currently leave this as zero, virtqueues have
+	 * implicit notifications.
 	 *
-	 * The third argument is a "struct hv_ops" containing the
put_chars()
-	 * get_chars(), notifier_add() and notifier_del() pointers.
-	 * The final argument is the output buffer size: we can do any size,
-	 * so we put PAGE_SIZE here. */
+	 * The third argument is a "struct hv_ops" containing the
+	 * put_chars(), get_chars(), notifier_add() and notifier_del()
+	 * pointers.  The final argument is the output buffer size: we
+	 * can do any size, so we put PAGE_SIZE here.
+	 */
 	hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);
 	if (IS_ERR(hvc)) {
 		err = PTR_ERR(hvc);
diff --git a/include/linux/virtio_console.h b/include/linux/virtio_console.h
index fe88517..9e0da40 100644
--- a/include/linux/virtio_console.h
+++ b/include/linux/virtio_console.h
@@ -3,8 +3,10 @@
 #include <linux/types.h>
 #include <linux/virtio_ids.h>
 #include <linux/virtio_config.h>
-/* This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so
- * anyone can use the definitions to implement compatible drivers/servers. */
+/*
+ * This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so
+ * anyone can use the definitions to implement compatible drivers/servers.
+ */
 
 /* Feature bits */
 #define VIRTIO_CONSOLE_F_SIZE	0	/* Does host provide console size? */
-- 
1.6.2.5

From: Rusty Russell <rusty at rustcorp.com.au>

That way, we can make it const as is good kernel style.  We use a separate
indirection for the early console, rather than mugging ops.put_chars.

We rename it hv_ops, too.

Signed-off-by: Rusty Russell <rusty at rustcorp.com.au>
Signed-off-by: Amit Shah <amit.shah at redhat.com>
---
 drivers/char/virtio_console.c |   60 +++++++++++++++++++++++-----------------
 1 files changed, 34 insertions(+), 26 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 26e238c..1d844a4 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -28,12 +28,12 @@ static struct virtio_device *vdev;
 static unsigned int in_len;
 static char *in, *inbuf;
 
-/* The operations for our console. */
-static struct hv_ops virtio_cons;
-
 /* The hvc device */
 static struct hvc_struct *hvc;
 
+/* This is the very early arch-specified put chars function. */
+static int (*early_put_chars)(u32, const char *, int);
+
 /*
  * The put_chars() callback is pretty straightforward.
  *
@@ -47,6 +47,9 @@ static int put_chars(u32 vtermno, const char *buf, int count)
 	struct scatterlist sg[1];
 	unsigned int len;
 
+	if (unlikely(early_put_chars))
+		return early_put_chars(vtermno, buf, count);
+
 	/* This is a convenient routine to initialize a single-elem sg list */
 	sg_init_one(sg, buf, count);
 
@@ -118,21 +121,6 @@ static int get_chars(u32 vtermno, char *buf, int count)
 }
 
 /*
- * Console drivers are initialized very early so boot messages can go
- * out, so we do things slightly differently from the generic virtio
- * initialization of the net and block drivers.
- *
- * At this stage, the console is output-only.  It's too early to set
- * up a virtqueue, so we let the drivers do some boutique early-output
- * thing.
- */
-int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
-{
-	virtio_cons.put_chars = put_chars;
-	return hvc_instantiate(0, 0, &virtio_cons);
-}
-
-/*
  * virtio console configuration. This supports:
  * - console resize
  */
@@ -174,6 +162,30 @@ static void hvc_handle_input(struct virtqueue *vq)
 		hvc_kick();
 }
 
+/* The operations for the console. */
+static struct hv_ops hv_ops = {
+	.get_chars = get_chars,
+	.put_chars = put_chars,
+	.notifier_add = notifier_add_vio,
+	.notifier_del = notifier_del_vio,
+	.notifier_hangup = notifier_del_vio,
+};
+
+/*
+ * Console drivers are initialized very early so boot messages can go
+ * out, so we do things slightly differently from the generic virtio
+ * initialization of the net and block drivers.
+ *
+ * At this stage, the console is output-only.  It's too early to set
+ * up a virtqueue, so we let the drivers do some boutique early-output
+ * thing.
+ */
+int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
+{
+	early_put_chars = put_chars;
+	return hvc_instantiate(0, 0, &hv_ops);
+}
+
 /*
  * Once we're further in boot, we get probed like any other virtio
  * device.  At this stage we set up the output virtqueue.
@@ -209,13 +221,6 @@ static int __devinit virtcons_probe(struct virtio_device
*dev)
 	in_vq = vqs[0];
 	out_vq = vqs[1];
 
-	/* Start using the new console output. */
-	virtio_cons.get_chars = get_chars;
-	virtio_cons.put_chars = put_chars;
-	virtio_cons.notifier_add = notifier_add_vio;
-	virtio_cons.notifier_del = notifier_del_vio;
-	virtio_cons.notifier_hangup = notifier_del_vio;
-
 	/*
 	 * The first argument of hvc_alloc() is the virtual console
 	 * number, so we use zero.  The second argument is the
@@ -228,7 +233,7 @@ static int __devinit virtcons_probe(struct virtio_device
*dev)
 	 * pointers.  The final argument is the output buffer size: we
 	 * can do any size, so we put PAGE_SIZE here.
 	 */
-	hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);
+	hvc = hvc_alloc(0, 0, &hv_ops, PAGE_SIZE);
 	if (IS_ERR(hvc)) {
 		err = PTR_ERR(hvc);
 		goto free_vqs;
@@ -236,6 +241,9 @@ static int __devinit virtcons_probe(struct virtio_device
*dev)
 
 	/* Register the input buffer the first time. */
 	add_inbuf();
+
+	/* Start using the new console output. */
+	early_put_chars = NULL;
 	return 0;
 
 free_vqs:
-- 
1.6.2.5