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

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Message-ID: <Yz8hIY9XdlycXE+N@google.com>
Date:   Thu, 6 Oct 2022 18:40:33 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Santosh Shukla <santosh.shukla@....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 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.

[*] https://lore.kernel.org/all/20220919093453.71737-1-likexu@tencent.com