* [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT
@ 2012-08-12 13:12 Gleb Natapov
2012-08-12 13:22 ` Avi Kivity
2012-08-13 22:07 ` Marcelo Tosatti
0 siblings, 2 replies; 7+ messages in thread
From: Gleb Natapov @ 2012-08-12 13:12 UTC (permalink / raw)
To: kvm; +Cc: avi, mtosatti
MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT. Restore it to the correct
value.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cc8ad98..d0f4bec 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6222,6 +6222,7 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
+ unsigned long debugctlmsr;
if (is_guest_mode(vcpu) && !vmx->nested.nested_run_pending) {
struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
@@ -6261,6 +6262,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
vmx_set_interrupt_shadow(vcpu, 0);
atomic_switch_perf_msrs(vmx);
+ debugctlmsr = get_debugctlmsr();
vmx->__launched = vmx->loaded_vmcs->launched;
asm(
@@ -6362,6 +6364,10 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
#endif
);
+ /* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */
+ if (debugctlmsr)
+ update_debugctlmsr(debugctlmsr);
+
#ifndef CONFIG_X86_64
/*
* The sysexit path does not restore ds/es, so we must set them to
--
Gleb.
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT
2012-08-12 13:12 [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT Gleb Natapov
@ 2012-08-12 13:22 ` Avi Kivity
2012-08-12 13:25 ` Gleb Natapov
2012-08-13 22:07 ` Marcelo Tosatti
1 sibling, 1 reply; 7+ messages in thread
From: Avi Kivity @ 2012-08-12 13:22 UTC (permalink / raw)
To: Gleb Natapov; +Cc: kvm, mtosatti
On 08/12/2012 04:12 PM, Gleb Natapov wrote:
> MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT. Restore it to the correct
> value.
>
> @@ -6222,6 +6222,7 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
> static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
> {
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> + unsigned long debugctlmsr;
>
> if (is_guest_mode(vcpu) && !vmx->nested.nested_run_pending) {
> struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> @@ -6261,6 +6262,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
> vmx_set_interrupt_shadow(vcpu, 0);
>
> atomic_switch_perf_msrs(vmx);
> + debugctlmsr = get_debugctlmsr();
How expensive is this? We may want a follow-on patch to cache it in a
per-cpu variable.
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT
2012-08-12 13:22 ` Avi Kivity
@ 2012-08-12 13:25 ` Gleb Natapov
2012-08-12 13:40 ` Avi Kivity
0 siblings, 1 reply; 7+ messages in thread
From: Gleb Natapov @ 2012-08-12 13:25 UTC (permalink / raw)
To: Avi Kivity; +Cc: kvm, mtosatti
On Sun, Aug 12, 2012 at 04:22:59PM +0300, Avi Kivity wrote:
> On 08/12/2012 04:12 PM, Gleb Natapov wrote:
> > MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT. Restore it to the correct
> > value.
> >
> > @@ -6222,6 +6222,7 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
> > static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
> > {
> > struct vcpu_vmx *vmx = to_vmx(vcpu);
> > + unsigned long debugctlmsr;
> >
> > if (is_guest_mode(vcpu) && !vmx->nested.nested_run_pending) {
> > struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> > @@ -6261,6 +6262,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
> > vmx_set_interrupt_shadow(vcpu, 0);
> >
> > atomic_switch_perf_msrs(vmx);
> > + debugctlmsr = get_debugctlmsr();
>
> How expensive is this? We may want a follow-on patch to cache it in a
> per-cpu variable.
>
I have patches ready. I couldn't measure any overhead of the
rdmsr(MSR_IA32_DEBUGCTLMSR).
--
Gleb.
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT
2012-08-12 13:25 ` Gleb Natapov
@ 2012-08-12 13:40 ` Avi Kivity
2012-08-12 17:28 ` Gleb Natapov
0 siblings, 1 reply; 7+ messages in thread
From: Avi Kivity @ 2012-08-12 13:40 UTC (permalink / raw)
To: Gleb Natapov; +Cc: kvm, mtosatti
On 08/12/2012 04:25 PM, Gleb Natapov wrote:
>> How expensive is this? We may want a follow-on patch to cache it in a
>> per-cpu variable.
>>
> I have patches ready. I couldn't measure any overhead of the
> rdmsr(MSR_IA32_DEBUGCTLMSR).
>
Do you mean while running kvm? How about just running it in a loop?
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT
2012-08-12 13:40 ` Avi Kivity
@ 2012-08-12 17:28 ` Gleb Natapov
2012-08-13 7:55 ` Avi Kivity
0 siblings, 1 reply; 7+ messages in thread
From: Gleb Natapov @ 2012-08-12 17:28 UTC (permalink / raw)
To: Avi Kivity; +Cc: kvm, mtosatti
On Sun, Aug 12, 2012 at 04:40:48PM +0300, Avi Kivity wrote:
> On 08/12/2012 04:25 PM, Gleb Natapov wrote:
>
> >> How expensive is this? We may want a follow-on patch to cache it in a
> >> per-cpu variable.
> >>
> > I have patches ready. I couldn't measure any overhead of the
> > rdmsr(MSR_IA32_DEBUGCTLMSR).
> >
>
> Do you mean while running kvm? How about just running it in a loop?
>
No, I mean running it in a loop. Loop with or without
rdmsr(MSR_IA32_DEBUGCTLMSR) takes the same time as measured by rdtsc.
--
Gleb.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT
2012-08-12 17:28 ` Gleb Natapov
@ 2012-08-13 7:55 ` Avi Kivity
0 siblings, 0 replies; 7+ messages in thread
From: Avi Kivity @ 2012-08-13 7:55 UTC (permalink / raw)
To: Gleb Natapov; +Cc: kvm, mtosatti
On 08/12/2012 08:28 PM, Gleb Natapov wrote:
> On Sun, Aug 12, 2012 at 04:40:48PM +0300, Avi Kivity wrote:
>> On 08/12/2012 04:25 PM, Gleb Natapov wrote:
>>
>> >> How expensive is this? We may want a follow-on patch to cache it in a
>> >> per-cpu variable.
>> >>
>> > I have patches ready. I couldn't measure any overhead of the
>> > rdmsr(MSR_IA32_DEBUGCTLMSR).
>> >
>>
>> Do you mean while running kvm? How about just running it in a loop?
>>
> No, I mean running it in a loop. Loop with or without
> rdmsr(MSR_IA32_DEBUGCTLMSR) takes the same time as measured by rdtsc.
Ok, good.
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT
2012-08-12 13:12 [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT Gleb Natapov
2012-08-12 13:22 ` Avi Kivity
@ 2012-08-13 22:07 ` Marcelo Tosatti
1 sibling, 0 replies; 7+ messages in thread
From: Marcelo Tosatti @ 2012-08-13 22:07 UTC (permalink / raw)
To: Gleb Natapov; +Cc: kvm, avi
On Sun, Aug 12, 2012 at 04:12:29PM +0300, Gleb Natapov wrote:
> MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT. Restore it to the correct
> value.
>
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
Applied, thanks.
^ permalink raw reply [flat|nested] 7+ messages in thread
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2012-08-12 13:12 [PATCH] KVM: vmx: restore MSR_IA32_DEBUGCTLMSR after VMEXIT Gleb Natapov
2012-08-12 13:22 ` Avi Kivity
2012-08-12 13:25 ` Gleb Natapov
2012-08-12 13:40 ` Avi Kivity
2012-08-12 17:28 ` Gleb Natapov
2012-08-13 7:55 ` Avi Kivity
2012-08-13 22:07 ` Marcelo Tosatti
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