linux-kernel - Re: [PATCH] KVM: SVM: vNMI pending bit is V_NMI_PENDING_MASK not V_NMI_BLOCKING

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Message-ID: <af74ae7c-ae81-38ed-97bb-75e39088d4ef@maciej.szmigiero.name>
Date:   Thu, 1 Jun 2023 19:53:57 +0200
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Maxim Levitsky <mlevitsk@...hat.com>,
        Santosh Shukla <santosh.shukla@....com>, vkuznets@...hat.com,
        jmattson@...gle.com, thomas.lendacky@....com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: SVM: vNMI pending bit is V_NMI_PENDING_MASK not
 V_NMI_BLOCKING_MASK

On 19.05.2023 17:51, Sean Christopherson wrote:
> On Fri, May 19, 2023, Maciej S. Szmigiero wrote:
>> From: "Maciej S. Szmigiero" <maciej.szmigiero@...cle.com>
>>
>> While testing Hyper-V enabled Windows Server 2019 guests on Zen4 hardware
>> I noticed that with vCPU count large enough (> 16) they sometimes froze at
>> boot.
>> With vCPU count of 64 they never booted successfully - suggesting some kind
>> of a race condition.
>>
>> Since adding "vnmi=0" module parameter made these guests boot successfully
>> it was clear that the problem is most likely (v)NMI-related.
>>
>> Running kvm-unit-tests quickly showed failing NMI-related tests cases, like
>> "multiple nmi" and "pending nmi" from apic-split, x2apic and xapic tests
>> and the NMI parts of eventinj test.
>>
>> The issue was that once one NMI was being serviced no other NMI was allowed
>> to be set pending (NMI limit = 0), which was traced to
>> svm_is_vnmi_pending() wrongly testing for the "NMI blocked" flag rather
>> than for the "NMI pending" flag.
>>
>> Fix this by testing for the right flag in svm_is_vnmi_pending().
>> Once this is done, the NMI-related kvm-unit-tests pass successfully and
>> the Windows guest no longer freezes at boot.
>>
>> Fixes: fa4c027a7956 ("KVM: x86: Add support for SVM's Virtual NMI")
>> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
> 
> Reviewed-by: Sean Christopherson <seanjc@...gle.com>
> 

I can't see this in kvm/kvm.git trees or the kvm-x86 ones on GitHub -
is this patch planned to be picked up for -rc5 soon?

Technically, just knowing the final commit id would be sufficit for my
purposes.

Thanks,
Maciej