2021-07-22 12:31:28

by Vitaly Kuznetsov

Subject: [PATCH] KVM: x86: Check the right feature bit for MSR_KVM_ASYNC_PF_ACK access

MSR_KVM_ASYNC_PF_ACK MSR is part of interrupt based asynchronous page fault
interface and not the original (deprecated) KVM_FEATURE_ASYNC_PF. This is
stated in Documentation/virt/kvm/msr.rst.

Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
arch/x86/kvm/x86.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d715ae9f9108..88ff7a1af198 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3406,7 +3406,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
break;
case MSR_KVM_ASYNC_PF_ACK:
- if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
+ if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
return 1;
if (data & 0x1) {
vcpu->arch.apf.pageready_pending = false;
@@ -3745,7 +3745,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
msr_info->data = vcpu->arch.apf.msr_int_val;
break;
case MSR_KVM_ASYNC_PF_ACK:
- if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
+ if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
return 1;

msr_info->data = 0;
--
2.31.1

2021-07-22 12:41:11

by Maxim Levitsky

Subject: Re: [PATCH] KVM: x86: Check the right feature bit for MSR_KVM_ASYNC_PF_ACK access

On Thu, 2021-07-22 at 14:30 +0200, Vitaly Kuznetsov wrote:
> MSR_KVM_ASYNC_PF_ACK MSR is part of interrupt based asynchronous page fault
> interface and not the original (deprecated) KVM_FEATURE_ASYNC_PF. This is
> stated in Documentation/virt/kvm/msr.rst.
>
> Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
> ---
> arch/x86/kvm/x86.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d715ae9f9108..88ff7a1af198 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3406,7 +3406,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> return 1;
> break;
> case MSR_KVM_ASYNC_PF_ACK:
> - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
> + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
> return 1;
> if (data & 0x1) {
> vcpu->arch.apf.pageready_pending = false;
> @@ -3745,7 +3745,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> msr_info->data = vcpu->arch.apf.msr_int_val;
> break;
> case MSR_KVM_ASYNC_PF_ACK:
> - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
> + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
> return 1;
>
> msr_info->data = 0;

Reviewed-by: Maxim Levitsky <[email protected]>

Best regards,
Maxim Levitsky

2021-07-22 15:41:38

by Oliver Upton

Subject: Re: [PATCH] KVM: x86: Check the right feature bit for MSR_KVM_ASYNC_PF_ACK access

On Thu, Jul 22, 2021 at 5:39 AM Maxim Levitsky <[email protected]> wrote:
>
> On Thu, 2021-07-22 at 14:30 +0200, Vitaly Kuznetsov wrote:
> > MSR_KVM_ASYNC_PF_ACK MSR is part of interrupt based asynchronous page fault
> > interface and not the original (deprecated) KVM_FEATURE_ASYNC_PF. This is
> > stated in Documentation/virt/kvm/msr.rst.
> >
> > Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
> > Signed-off-by: Vitaly Kuznetsov <[email protected]>
> > ---
> > arch/x86/kvm/x86.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index d715ae9f9108..88ff7a1af198 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -3406,7 +3406,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > return 1;
> > break;
> > case MSR_KVM_ASYNC_PF_ACK:
> > - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
> > + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
> > return 1;
> > if (data & 0x1) {
> > vcpu->arch.apf.pageready_pending = false;
> > @@ -3745,7 +3745,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > msr_info->data = vcpu->arch.apf.msr_int_val;
> > break;
> > case MSR_KVM_ASYNC_PF_ACK:
> > - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
> > + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
> > return 1;
> >
> > msr_info->data = 0;
>
> Reviewed-by: Maxim Levitsky <[email protected]>
>
> Best regards,
> Maxim Levitsky
>

Reviewed-by: Oliver Upton <[email protected]>

--
Thanks,
Oliver

2021-07-22 17:25:00

by Sean Christopherson

Subject: Re: [PATCH] KVM: x86: Check the right feature bit for MSR_KVM_ASYNC_PF_ACK access

On Thu, Jul 22, 2021, Vitaly Kuznetsov wrote:
> MSR_KVM_ASYNC_PF_ACK MSR is part of interrupt based asynchronous page fault
> interface and not the original (deprecated) KVM_FEATURE_ASYNC_PF. This is
> stated in Documentation/virt/kvm/msr.rst.
>
> Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
> ---
> arch/x86/kvm/x86.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d715ae9f9108..88ff7a1af198 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3406,7 +3406,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> return 1;
> break;
> case MSR_KVM_ASYNC_PF_ACK:
> - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
> + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))

Do we want to require both, or do we want to let userspace be stupid?

> return 1;
> if (data & 0x1) {
> vcpu->arch.apf.pageready_pending = false;
> @@ -3745,7 +3745,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> msr_info->data = vcpu->arch.apf.msr_int_val;
> break;
> case MSR_KVM_ASYNC_PF_ACK:
> - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
> + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
> return 1;
>
> msr_info->data = 0;
> --
> 2.31.1
>

2021-07-23 07:00:33

by Vitaly Kuznetsov

Subject: Re: [PATCH] KVM: x86: Check the right feature bit for MSR_KVM_ASYNC_PF_ACK access

Sean Christopherson <[email protected]> writes:

> On Thu, Jul 22, 2021, Vitaly Kuznetsov wrote:
>> MSR_KVM_ASYNC_PF_ACK MSR is part of interrupt based asynchronous page fault
>> interface and not the original (deprecated) KVM_FEATURE_ASYNC_PF. This is
>> stated in Documentation/virt/kvm/msr.rst.
>>
>> Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
>> Signed-off-by: Vitaly Kuznetsov <[email protected]>
>> ---
>> arch/x86/kvm/x86.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index d715ae9f9108..88ff7a1af198 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -3406,7 +3406,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> return 1;
>> break;
>> case MSR_KVM_ASYNC_PF_ACK:
>> - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
>> + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
>
> Do we want to require both, or do we want to let userspace be stupid?
>

It's OK to be stupid :-)

Thinking more about it, I'd suggest we go the other way around: allow
access to MSR_KVM_ASYNC_PF_EN when either KVM_FEATURE_ASYNC_PF or
KVM_FEATURE_ASYNC_PF_INT are present. This will allow to eventually
deprecate KVM_FEATURE_ASYNC_PF completely and switch to
KVM_FEATURE_ASYNC_PF_INT exclusively.

>> return 1;
>> if (data & 0x1) {
>> vcpu->arch.apf.pageready_pending = false;
>> @@ -3745,7 +3745,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> msr_info->data = vcpu->arch.apf.msr_int_val;
>> break;
>> case MSR_KVM_ASYNC_PF_ACK:
>> - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
>> + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
>> return 1;
>>
>> msr_info->data = 0;
>> --
>> 2.31.1
>>
>

--
Vitaly

2021-07-26 12:31:18

by Paolo Bonzini

Subject: Re: [PATCH] KVM: x86: Check the right feature bit for MSR_KVM_ASYNC_PF_ACK access

On 22/07/21 14:30, Vitaly Kuznetsov wrote:
> MSR_KVM_ASYNC_PF_ACK MSR is part of interrupt based asynchronous page fault
> interface and not the original (deprecated) KVM_FEATURE_ASYNC_PF. This is
> stated in Documentation/virt/kvm/msr.rst.
>
> Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
> ---
> arch/x86/kvm/x86.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d715ae9f9108..88ff7a1af198 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3406,7 +3406,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> return 1;
> break;
> case MSR_KVM_ASYNC_PF_ACK:
> - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
> + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
> return 1;
> if (data & 0x1) {
> vcpu->arch.apf.pageready_pending = false;
> @@ -3745,7 +3745,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> msr_info->data = vcpu->arch.apf.msr_int_val;
> break;
> case MSR_KVM_ASYNC_PF_ACK:
> - if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF))
> + if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT))
> return 1;
>
> msr_info->data = 0;
>

Queued, thanks.

Paolo