2019-08-27 16:05:43

by Vitaly Kuznetsov

Subject: [PATCH 3/3] KVM: x86: announce KVM_CAP_HYPERV_ENLIGHTENED_VMCS support only when it is available

It was discovered that after commit 65efa61dc0d5 ("selftests: kvm: provide
common function to enable eVMCS") hyperv_cpuid selftest is failing on AMD.
The reason is that the commit changed _vcpu_ioctl() to vcpu_ioctl() in the
test and this one can't fail.

Instead of fixing the test is seems to make more sense to not announce
KVM_CAP_HYPERV_ENLIGHTENED_VMCS support if it is definitely missing
(on svm and in case kvm_intel.nested=0).

Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
arch/x86/kvm/x86.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d1cd0fcff9e7..ef2e8b138300 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3106,7 +3106,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_HYPERV_EVENTFD:
case KVM_CAP_HYPERV_TLBFLUSH:
case KVM_CAP_HYPERV_SEND_IPI:
- case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
case KVM_CAP_HYPERV_CPUID:
case KVM_CAP_PCI_SEGMENT:
case KVM_CAP_DEBUGREGS:
@@ -3183,6 +3182,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
r = kvm_x86_ops->get_nested_state ?
kvm_x86_ops->get_nested_state(NULL, NULL, 0) : 0;
break;
+ case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
+ r = kvm_x86_ops->nested_enable_evmcs != NULL;
default:
break;
}
--
2.20.1

2019-08-27 16:56:26

by Jim Mattson

Subject: Re: [PATCH 3/3] KVM: x86: announce KVM_CAP_HYPERV_ENLIGHTENED_VMCS support only when it is available

On Tue, Aug 27, 2019 at 9:04 AM Vitaly Kuznetsov <[email protected]> wrote:
>
> It was discovered that after commit 65efa61dc0d5 ("selftests: kvm: provide
> common function to enable eVMCS") hyperv_cpuid selftest is failing on AMD.
> The reason is that the commit changed _vcpu_ioctl() to vcpu_ioctl() in the
> test and this one can't fail.
>
> Instead of fixing the test is seems to make more sense to not announce
> KVM_CAP_HYPERV_ENLIGHTENED_VMCS support if it is definitely missing
> (on svm and in case kvm_intel.nested=0).
>
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
> ---
> arch/x86/kvm/x86.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d1cd0fcff9e7..ef2e8b138300 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3106,7 +3106,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_HYPERV_EVENTFD:
> case KVM_CAP_HYPERV_TLBFLUSH:
> case KVM_CAP_HYPERV_SEND_IPI:
> - case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
> case KVM_CAP_HYPERV_CPUID:
> case KVM_CAP_PCI_SEGMENT:
> case KVM_CAP_DEBUGREGS:
> @@ -3183,6 +3182,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> r = kvm_x86_ops->get_nested_state ?
> kvm_x86_ops->get_nested_state(NULL, NULL, 0) : 0;
> break;
> + case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
> + r = kvm_x86_ops->nested_enable_evmcs != NULL;

You should probably have an explicit break here, in case someone later
adds another case below.

> default:
> break;
> }
> --
> 2.20.1
>

2019-08-27 19:54:14

by Sean Christopherson

Subject: Re: [PATCH 3/3] KVM: x86: announce KVM_CAP_HYPERV_ENLIGHTENED_VMCS support only when it is available

On Tue, Aug 27, 2019 at 09:54:39AM -0700, Jim Mattson wrote:
> On Tue, Aug 27, 2019 at 9:04 AM Vitaly Kuznetsov <[email protected]> wrote:
> >
> > It was discovered that after commit 65efa61dc0d5 ("selftests: kvm: provide
> > common function to enable eVMCS") hyperv_cpuid selftest is failing on AMD.
> > The reason is that the commit changed _vcpu_ioctl() to vcpu_ioctl() in the
> > test and this one can't fail.
> >
> > Instead of fixing the test is seems to make more sense to not announce
> > KVM_CAP_HYPERV_ENLIGHTENED_VMCS support if it is definitely missing
> > (on svm and in case kvm_intel.nested=0).
> >
> > Signed-off-by: Vitaly Kuznetsov <[email protected]>
> > ---
> > arch/x86/kvm/x86.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index d1cd0fcff9e7..ef2e8b138300 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -3106,7 +3106,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> > case KVM_CAP_HYPERV_EVENTFD:
> > case KVM_CAP_HYPERV_TLBFLUSH:
> > case KVM_CAP_HYPERV_SEND_IPI:
> > - case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
> > case KVM_CAP_HYPERV_CPUID:
> > case KVM_CAP_PCI_SEGMENT:
> > case KVM_CAP_DEBUGREGS:
> > @@ -3183,6 +3182,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> > r = kvm_x86_ops->get_nested_state ?
> > kvm_x86_ops->get_nested_state(NULL, NULL, 0) : 0;
> > break;
> > + case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
> > + r = kvm_x86_ops->nested_enable_evmcs != NULL;
>
> You should probably have an explicit break here, in case someone later
> adds another case below.

Yep, this will trigger a warning on compilers with -Wimplicit-fallthrough.

2019-08-28 07:31:42

by Vitaly Kuznetsov

Subject: Re: [PATCH 3/3] KVM: x86: announce KVM_CAP_HYPERV_ENLIGHTENED_VMCS support only when it is available

Sean Christopherson <[email protected]> writes:

> On Tue, Aug 27, 2019 at 09:54:39AM -0700, Jim Mattson wrote:
>> On Tue, Aug 27, 2019 at 9:04 AM Vitaly Kuznetsov <[email protected]> wrote:
>> >
>> > It was discovered that after commit 65efa61dc0d5 ("selftests: kvm: provide
>> > common function to enable eVMCS") hyperv_cpuid selftest is failing on AMD.
>> > The reason is that the commit changed _vcpu_ioctl() to vcpu_ioctl() in the
>> > test and this one can't fail.
>> >
>> > Instead of fixing the test is seems to make more sense to not announce
>> > KVM_CAP_HYPERV_ENLIGHTENED_VMCS support if it is definitely missing
>> > (on svm and in case kvm_intel.nested=0).
>> >
>> > Signed-off-by: Vitaly Kuznetsov <[email protected]>
>> > ---
>> > arch/x86/kvm/x86.c | 3 ++-
>> > 1 file changed, 2 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> > index d1cd0fcff9e7..ef2e8b138300 100644
>> > --- a/arch/x86/kvm/x86.c
>> > +++ b/arch/x86/kvm/x86.c
>> > @@ -3106,7 +3106,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>> > case KVM_CAP_HYPERV_EVENTFD:
>> > case KVM_CAP_HYPERV_TLBFLUSH:
>> > case KVM_CAP_HYPERV_SEND_IPI:
>> > - case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
>> > case KVM_CAP_HYPERV_CPUID:
>> > case KVM_CAP_PCI_SEGMENT:
>> > case KVM_CAP_DEBUGREGS:
>> > @@ -3183,6 +3182,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>> > r = kvm_x86_ops->get_nested_state ?
>> > kvm_x86_ops->get_nested_state(NULL, NULL, 0) : 0;
>> > break;
>> > + case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
>> > + r = kvm_x86_ops->nested_enable_evmcs != NULL;
>>
>> You should probably have an explicit break here, in case someone later
>> adds another case below.
>
> Yep, this will trigger a warning on compilers with -Wimplicit-fallthrough.

I always forget there's more than checkpatch.pl :-) Thanks you your
reviews guys, I'm going to send v2 of this patchset without PATCH1 which
was already queued by Radim.

--
Vitaly