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From:   Wei Zhang <zhanwei@google.com>
Date:   Mon, 16 May 2022 21:30:00 +0200
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Subject: Re: [PATCH 0/2] KVM: x86: Fix incorrect VM-exit profiling
To:     Sean Christopherson <seanjc@google.com>,
        Suleiman Souhlal <suleiman@google.com>
Cc:     Sangwhan Moon <sxm@google.com>, Ingo Molnar <mingo@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Jing Zhang <jingzhangos@google.com>,
        David Matlack <dmatlack@google.com>
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> Please don't top-post.  From https://people.kernel.org/tglx/notes-about-netiquette:

Ah, I didn't know this should be avoided. Thanks for the info!

> My preference would be to find a more complete, KVM-specific solution.  The
> profiling stuff seems like it's a dead end, i.e. will always be flawed in some
> way.  If this cleanup didn't require a new hypercall then I wouldn't care, but
> I don't love having to extend KVM's guest/host ABI for something that ideally
> will become obsolete sooner than later.

I also feel that adding a new hypercall is too much here. A
KVM-specific solution is definitely better, and the eBPF based
approach you mentioned sounds like the ultimate solution (at least for
inspecting exit reasons).

+Suleiman What do you think? The on-going work Sean described sounds
promising, perhaps we should put this patch aside for the time being.