From: "Shukla, Santosh" <santosh.shukla@amd.com>
To: Maxim Levitsky <mlevitsk@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Tom Lendacky <thomas.lendacky@amd.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/7] KVM: SVM: Report NMI not allowed when Guest busy handling VNMI
Date: Thu, 21 Jul 2022 15:01:01 +0530 [thread overview]
Message-ID: <ca108529-9252-5f1d-cbd1-51a43b476ce9@amd.com> (raw)
In-Reply-To: <76e007d7fc7af0629279f2563f8d0c48274bc774.camel@redhat.com>
On 7/10/2022 9:38 PM, Maxim Levitsky wrote:
> On Fri, 2022-06-17 at 20:29 +0530, Shukla, Santosh wrote:
>>
>> On 6/7/2022 6:42 PM, Maxim Levitsky wrote:
>>> On Tue, 2022-06-07 at 16:10 +0300, Maxim Levitsky wrote:
>>>> On Thu, 2022-06-02 at 19:56 +0530, Santosh Shukla wrote:
>>>>> In the VNMI case, Report NMI is not allowed when the processor set the
>>>>> V_NMI_MASK to 1 which means the Guest is busy handling VNMI.
>>>>>
>>>>> Signed-off-by: Santosh Shukla <santosh.shukla@amd.com>
>>>>> ---
>>>>> arch/x86/kvm/svm/svm.c | 6 ++++++
>>>>> 1 file changed, 6 insertions(+)
>>>>>
>>>>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
>>>>> index d67a54517d95..a405e414cae4 100644
>>>>> --- a/arch/x86/kvm/svm/svm.c
>>>>> +++ b/arch/x86/kvm/svm/svm.c
>>>>> @@ -3483,6 +3483,9 @@ bool svm_nmi_blocked(struct kvm_vcpu *vcpu)
>>>>> struct vmcb *vmcb = svm->vmcb;
>>>>> bool ret;
>>>>>
>>>>> + if (is_vnmi_enabled(vmcb) && is_vnmi_mask_set(vmcb))
>>>>> + return true;
>>>>
>>>> How does this interact with GIF? if the guest does clgi, will the
>>>> CPU update the V_NMI_MASK on its own If vGIF is enabled?
>>>>
>> Yes.
>>
>>>> What happens if vGIF is disabled and vNMI is enabled? KVM then intercepts
>>>> the stgi/clgi, and it should then update the V_NMI_MASK?
>>>>
>> No.
>>
>> For both case - HW takes the V_NMI event at the boundary of VMRUN instruction.
>
> How that is possible? if vGIF is disabled in L1, then L1 can't execute STGI/CLGI -
> that means that the CPU can't update the V_NMI, as it never sees the STGI/CLGI
> beeing executed.
>
If vGIF is disabled then HW will take the vnmi event at the boundary of vmrun instruction.
Thanks,
Santosh
> Best regards,
> Maxim Levitsky
>
>>
>>>>
>>>>
>>>>> +
>>>>> if (!gif_set(svm))
>>>>> return true;
>>>>>
>>>>> @@ -3618,6 +3621,9 @@ static void svm_enable_nmi_window(struct kvm_vcpu *vcpu)
>>>>> {
>>>>> struct vcpu_svm *svm = to_svm(vcpu);
>>>>>
>>>>> + if (is_vnmi_enabled(svm->vmcb) && is_vnmi_mask_set(svm->vmcb))
>>>>> + return;
>>>>
>>>> This might have hidden assumption that we will only enable NMI window when vNMI is masked.
>>>
>>> Also what if vNMI is already pending?
>>>
>> If V_NMI_MASK set, that means V_NMI is pending, if so then inject another V_NMI in next VMRUN.
>>
>> Thanks,
>> Santosh
>>
>>> Best regards,
>>> Maxim Levitsky
>>>>
>>>>
>>>>> +
>>>>> if ((vcpu->arch.hflags & (HF_NMI_MASK | HF_IRET_MASK)) == HF_NMI_MASK)
>>>>> return; /* IRET will cause a vm exit */
>>>>>
>>>>
>>>> Best regards,
>>>> Maxim Levitsky
>
>
next prev parent reply other threads:[~2022-07-21 9:31 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-02 14:26 [PATCH 0/7] Virtual NMI feature Santosh Shukla
2022-06-02 14:26 ` [PATCH 1/7] x86/cpu: Add CPUID feature bit for VNMI Santosh Shukla
2022-06-07 12:32 ` Maxim Levitsky
2022-06-02 14:26 ` [PATCH 2/7] KVM: SVM: Add VNMI bit definition Santosh Shukla
2022-06-07 12:55 ` Maxim Levitsky
2022-06-17 14:42 ` Shukla, Santosh
2022-06-02 14:26 ` [PATCH 3/7] KVM: SVM: Add VNMI support in get/set_nmi_mask Santosh Shukla
2022-06-07 13:07 ` Maxim Levitsky
2022-06-17 14:45 ` Shukla, Santosh
2022-06-17 14:48 ` Shukla, Santosh
2022-07-10 16:09 ` Maxim Levitsky
2022-07-21 9:25 ` Shukla, Santosh
2022-07-10 18:39 ` Maxim Levitsky
2022-06-02 14:26 ` [PATCH 4/7] KVM: SVM: Report NMI not allowed when Guest busy handling VNMI Santosh Shukla
2022-06-07 13:10 ` Maxim Levitsky
2022-06-07 13:12 ` Maxim Levitsky
2022-06-17 14:59 ` Shukla, Santosh
2022-07-10 16:08 ` Maxim Levitsky
2022-07-21 9:31 ` Shukla, Santosh [this message]
2022-07-21 11:56 ` Maxim Levitsky
2022-06-02 14:26 ` [PATCH 5/7] KVM: SVM: Add VNMI support in inject_nmi Santosh Shukla
2022-06-07 13:14 ` Maxim Levitsky
2022-06-17 15:05 ` Shukla, Santosh
2022-07-10 16:07 ` Maxim Levitsky
2022-06-02 14:26 ` [PATCH 6/7] KVM: nSVM: implement nested VNMI Santosh Shukla
2022-06-07 13:22 ` Maxim Levitsky
2022-06-17 15:08 ` Shukla, Santosh
2022-06-02 14:26 ` [PATCH 7/7] KVM: SVM: Enable VNMI feature Santosh Shukla
2022-06-06 23:01 ` [PATCH 0/7] Virtual NMI feature Jim Mattson
2022-06-08 8:23 ` Shukla, Santosh
2022-09-05 19:45 ` Jim Mattson
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