linux-kernel - Re: [PATCHv4 0/8] Virtual NMI feature

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Date:   Sun, 16 Oct 2022 11:19:28 +0530
From:   Santosh Shukla <santosh.shukla@....com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, mlevitsk@...hat.com,
        mail@...iej.szmigiero.name
Subject: Re: [PATCHv4 0/8] Virtual NMI feature



On 10/10/2022 9:21 PM, Sean Christopherson wrote:
> On Mon, Oct 10, 2022, Santosh Shukla wrote:
>>
>>
>> On 10/7/2022 12:10 AM, Sean Christopherson wrote:
>>> On Mon, Aug 29, 2022, Santosh Shukla wrote:
>>>> If NMI virtualization enabled and NMI_INTERCEPT bit is unset
>>>> then HW will exit with #INVALID exit reason.
>>>>
>>>> To enable the VNMI capability, Hypervisor need to program
>>>> V_NMI_ENABLE bit 1.
>>>>
>>>> The presence of this feature is indicated via the CPUID function
>>>> 0x8000000A_EDX[25].
>>>
>>> Until there is publicly available documentation, I am not going to review this
>>> any further.  This goes for all new features, e.g. PerfMonv2[*].  I understand
>>> the need and desire to get code merged far in advance of hardware being available,
>>> but y'all clearly have specs, i.e. this is a very solvable problem.  Throw all the
>>> disclaimers you want on the specs to make it abundantly clear that they are for
>>> preview purposes or whatever, but reviewing KVM code without a spec just doesn't
>>> work for me.
>>>
>>
>> Sure Sean.
>>
>> I am told that the APM should be out in the next couple of weeks.
> 
> Probably too late to be of much value for virtual NMI support, but for future
> features, it would be very helpful to release "preview" documentation ASAP so that
> we don't have to wait for the next APM update, which IIUC only happens ~2 times a
> year.

Virtual NMI spec is at [1], Chapter - 15.21.10 NMI Virtualization.

Thanks,
Santosh
[1] https://www.amd.com/en/support/tech-docs/amd64-architecture-programmers-manual-volumes-1-5