Linux Virtualization - Feb 2020 - [PATCH] x86/ioperm: add new paravirt function update_io_bitmap

Commit 111e7b15cf10f6 ("x86/ioperm: Extend IOPL config to control
ioperm() as well") reworked the iopl syscall to use I/O bitmaps.

Unfortunately this broke Xen PV domains using that syscall as there
is currently no I/O bitmap support in PV domains.

Add I/O bitmap support via a new paravirt function update_io_bitmap
which Xen PV domains can use to update their I/O bitmaps via a
hypercall.

Fixes: 111e7b15cf10f6 ("x86/ioperm: Extend IOPL config to control ioperm()
as well")
Reported-by: Jan Beulich <jbeulich at suse.com>
Cc: <stable at vger.kernel.org> # 5.5
Signed-off-by: Juergen Gross <jgross at suse.com>
Reviewed-by: Jan Beulich <jbeulich at suse.com>
Tested-by: Jan Beulich <jbeulich at suse.com>
---
 arch/x86/include/asm/io_bitmap.h      |  9 ++++++++-
 arch/x86/include/asm/paravirt.h       |  7 +++++++
 arch/x86/include/asm/paravirt_types.h |  4 ++++
 arch/x86/kernel/paravirt.c            |  5 +++++
 arch/x86/kernel/process.c             |  2 +-
 arch/x86/xen/enlighten_pv.c           | 25 +++++++++++++++++++++++++
 6 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index 02c6ef8f7667..07344d82e88e 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -19,7 +19,14 @@ struct task_struct;
 void io_bitmap_share(struct task_struct *tsk);
 void io_bitmap_exit(void);
 
-void tss_update_io_bitmap(void);
+void native_tss_update_io_bitmap(void);
+
+#ifdef CONFIG_PARAVIRT_XXL
+#include <asm/paravirt.h>
+#else
+#define tss_update_io_bitmap native_tss_update_io_bitmap
+#endif
+
 #else
 static inline void io_bitmap_share(struct task_struct *tsk) { }
 static inline void io_bitmap_exit(void) { }
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 86e7317eb31f..694d8daf4983 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -295,6 +295,13 @@ static inline void write_idt_entry(gate_desc *dt, int
entry, const gate_desc *g)
 	PVOP_VCALL3(cpu.write_idt_entry, dt, entry, g);
 }
 
+#ifdef CONFIG_X86_IOPL_IOPERM
+static inline void tss_update_io_bitmap(void)
+{
+	PVOP_VCALL0(cpu.update_io_bitmap);
+}
+#endif
+
 static inline void paravirt_activate_mm(struct mm_struct *prev,
 					struct mm_struct *next)
 {
diff --git a/arch/x86/include/asm/paravirt_types.h
b/arch/x86/include/asm/paravirt_types.h
index 84812964d3dd..732f62e04ddb 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -140,6 +140,10 @@ struct pv_cpu_ops {
 
 	void (*load_sp0)(unsigned long sp0);
 
+#ifdef CONFIG_X86_IOPL_IOPERM
+	void (*update_io_bitmap)(void);
+#endif
+
 	void (*wbinvd)(void);
 
 	/* cpuid emulation, mostly so that caps bits can be disabled */
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 789f5e4f89de..c131ba4e70ef 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -30,6 +30,7 @@
 #include <asm/timer.h>
 #include <asm/special_insns.h>
 #include <asm/tlb.h>
+#include <asm/io_bitmap.h>
 
 /*
  * nop stub, which must not clobber anything *including the stack* to
@@ -341,6 +342,10 @@ struct paravirt_patch_template pv_ops = {
 	.cpu.iret		= native_iret,
 	.cpu.swapgs		= native_swapgs,
 
+#ifdef CONFIG_X86_IOPL_IOPERM
+	.cpu.update_io_bitmap	= native_tss_update_io_bitmap,
+#endif
+
 	.cpu.start_context_switch	= paravirt_nop,
 	.cpu.end_context_switch		= paravirt_nop,
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 839b5244e3b7..3053c85e0e42 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -374,7 +374,7 @@ static void tss_copy_io_bitmap(struct tss_struct *tss,
struct io_bitmap *iobm)
 /**
  * tss_update_io_bitmap - Update I/O bitmap before exiting to usermode
  */
-void tss_update_io_bitmap(void)
+void native_tss_update_io_bitmap(void)
 {
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
 	struct thread_struct *t = &current->thread;
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 1f756ffffe8b..feaf2e68ee5c 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -72,6 +72,9 @@
 #include <asm/mwait.h>
 #include <asm/pci_x86.h>
 #include <asm/cpu.h>
+#ifdef CONFIG_X86_IOPL_IOPERM
+#include <asm/io_bitmap.h>
+#endif
 
 #ifdef CONFIG_ACPI
 #include <linux/acpi.h>
@@ -837,6 +840,25 @@ static void xen_load_sp0(unsigned long sp0)
 	this_cpu_write(cpu_tss_rw.x86_tss.sp0, sp0);
 }
 
+#ifdef CONFIG_X86_IOPL_IOPERM
+static void xen_update_io_bitmap(void)
+{
+	struct physdev_set_iobitmap iobitmap;
+	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
+
+	native_tss_update_io_bitmap();
+
+	iobitmap.bitmap = (uint8_t *)(&tss->x86_tss) +
+			  tss->x86_tss.io_bitmap_base;
+	if (tss->x86_tss.io_bitmap_base == IO_BITMAP_OFFSET_INVALID)
+		iobitmap.nr_ports = 0;
+	else
+		iobitmap.nr_ports = IO_BITMAP_BITS;
+
+	HYPERVISOR_physdev_op(PHYSDEVOP_set_iobitmap, &iobitmap);
+}
+#endif
+
 static void xen_io_delay(void)
 {
 }
@@ -1046,6 +1068,9 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 	.write_idt_entry = xen_write_idt_entry,
 	.load_sp0 = xen_load_sp0,
 
+#ifdef CONFIG_X86_IOPL_IOPERM
+	.update_io_bitmap = xen_update_io_bitmap,
+#endif
 	.io_delay = xen_io_delay,
 
 	/* Xen takes care of %gs when switching to usermode for us */
-- 
2.16.4

Juergen Gross <jgross at suse.com> writes:
> Commit 111e7b15cf10f6 ("x86/ioperm: Extend IOPL config to control
> ioperm() as well") reworked the iopl syscall to use I/O bitmaps.
>
> Unfortunately this broke Xen PV domains using that syscall as there
> is currently no I/O bitmap support in PV domains.
>
> Add I/O bitmap support via a new paravirt function update_io_bitmap
> which Xen PV domains can use to update their I/O bitmaps via a
> hypercall.
>
> Fixes: 111e7b15cf10f6 ("x86/ioperm: Extend IOPL config to control
ioperm() as well")
> Reported-by: Jan Beulich <jbeulich at suse.com>
> Cc: <stable at vger.kernel.org> # 5.5
> Signed-off-by: Juergen Gross <jgross at suse.com>
> Reviewed-by: Jan Beulich <jbeulich at suse.com>
> Tested-by: Jan Beulich <jbeulich at suse.com>
Duh, sorry about that and thanks for fixing it.

BTW, why isn't stuff like this not catched during next or at least
before the final release? Is nothing running CI on upstream with all
that XEN muck active?

Thanks,

        tglx

On 18.02.20 22:03, Thomas Gleixner wrote:
> Juergen Gross <jgross at suse.com> writes:
>> Commit 111e7b15cf10f6 ("x86/ioperm: Extend IOPL config to control
>> ioperm() as well") reworked the iopl syscall to use I/O bitmaps.
>>
>> Unfortunately this broke Xen PV domains using that syscall as there
>> is currently no I/O bitmap support in PV domains.
>>
>> Add I/O bitmap support via a new paravirt function update_io_bitmap
>> which Xen PV domains can use to update their I/O bitmaps via a
>> hypercall.
>>
>> Fixes: 111e7b15cf10f6 ("x86/ioperm: Extend IOPL config to control
ioperm() as well")
>> Reported-by: Jan Beulich <jbeulich at suse.com>
>> Cc: <stable at vger.kernel.org> # 5.5
>> Signed-off-by: Juergen Gross <jgross at suse.com>
>> Reviewed-by: Jan Beulich <jbeulich at suse.com>
>> Tested-by: Jan Beulich <jbeulich at suse.com>
> 
> Duh, sorry about that and thanks for fixing it.
> 
> BTW, why isn't stuff like this not catched during next or at least
> before the final release? Is nothing running CI on upstream with all
> that XEN muck active?
This problem showed up by not being able to start the X server (probably
not the freshest one) in dom0 on a moderate aged AMD system.

Our CI tests tend do be more text console based for dom0.


Juergen