From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Oliver Upton <oupton@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: x86: Check the right feature bit for MSR_KVM_ASYNC_PF_ACK access
Date: Fri, 23 Jul 2021 08:58:33 +0200 [thread overview]
Message-ID: <87lf5x7bza.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <YPmopoGY4hwuVHAp@google.com>
Sean Christopherson <seanjc@google.com> 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 <vkuznets@redhat.com>
>> ---
>> 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
next prev parent reply other threads:[~2021-07-23 6:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-22 12:30 [PATCH] KVM: x86: Check the right feature bit for MSR_KVM_ASYNC_PF_ACK access Vitaly Kuznetsov
2021-07-22 12:39 ` Maxim Levitsky
2021-07-22 15:40 ` Oliver Upton
2021-07-22 17:19 ` Sean Christopherson
2021-07-23 6:58 ` Vitaly Kuznetsov [this message]
2021-07-26 12:27 ` Paolo Bonzini
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