Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1623180 > unrolled thread

[PATCH] KVM: nVMX: fix AD condition when handling EPT violation

Back to article view | Back to linux.kernel

Contents

  [PATCH] KVM: nVMX: fix AD condition when handling EPT violation Radim Krčmář <rkrcmar@redhat.com> - 2017-04-13 18:50 +0200
    Re: [PATCH] KVM: nVMX: fix AD condition when handling EPT violation Paolo Bonzini <pbonzini@redhat.com> - 2017-04-14 07:20 +0200
      Re: [PATCH] KVM: nVMX: fix AD condition when handling EPT violation Radim Krčmář <rkrcmar@redhat.com> - 2017-04-24 18:00 +0200

#1623180 — [PATCH] KVM: nVMX: fix AD condition when handling EPT violation

I have introduced this bug when applying and simplifying Paolo's patch
as we agreed on the list.  The original was "x &= ~y; if (z) x |= y;".

Here is the story of a bad workflow:

  A maintainer was already testing with the intended change, but it was
  applied only to a testing repo on a different machine.  When the time
  to push tested patches to kvm/next came, he realized that this change
  was missing and quickly added it to the maintenance repo, didn't test
  again (because the change is trivial, right), and pushed the world to
  fire.

Fixes: ae1e2d1082ae ("kvm: nVMX: support EPT accessed/dirty bits")
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 arch/x86/kvm/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cfdb0d9389d1..837f6dd1ae9c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6221,7 +6221,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
 		 * page table accesses are reads or writes.
 		 */
 		u64 eptp = nested_ept_get_cr3(vcpu);
-		if (eptp & VMX_EPT_AD_ENABLE_BIT)
+		if (!(eptp & VMX_EPT_AD_ENABLE_BIT))
 			exit_qualification &= ~EPT_VIOLATION_ACC_WRITE;
 	}
 
-- 
2.12.0

[toc] | [next] | [standalone]

#1623514

On 14/04/2017 00:39, Radim Krčmář wrote:
> I have introduced this bug when applying and simplifying Paolo's patch
> as we agreed on the list.  The original was "x &= ~y; if (z) x |= y;".
> 
> Here is the story of a bad workflow:
> 
>   A maintainer was already testing with the intended change, but it was
>   applied only to a testing repo on a different machine.  When the time
>   to push tested patches to kvm/next came, he realized that this change
>   was missing and quickly added it to the maintenance repo, didn't test
>   again (because the change is trivial, right), and pushed the world to
>   fire.
> 
> Fixes: ae1e2d1082ae ("kvm: nVMX: support EPT accessed/dirty bits")
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
>  arch/x86/kvm/vmx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index cfdb0d9389d1..837f6dd1ae9c 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6221,7 +6221,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
>  		 * page table accesses are reads or writes.
>  		 */
>  		u64 eptp = nested_ept_get_cr3(vcpu);
> -		if (eptp & VMX_EPT_AD_ENABLE_BIT)
> +		if (!(eptp & VMX_EPT_AD_ENABLE_BIT))
>  			exit_qualification &= ~EPT_VIOLATION_ACC_WRITE;
>  	}
>  
> 

I have done this as well, so you're forgiven. :)

More important: did kvm-unit-test catch the bug?

Paolo

[toc] | [prev] | [next] | [standalone]

#1629704

2017-04-14 13:10+0800, Paolo Bonzini:
> More important: did kvm-unit-test catch the bug?

It did;  the bright side. :)

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web