| Message ID | 20120812131228.GL3341@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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.
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. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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?
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. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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.
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. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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
MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT. Restore it to the correct value. Signed-off-by: Gleb Natapov <gleb@redhat.com> -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html