linux-kernel - Re: [PATCH 0/2] KVM: x86: Fix incorrect VM-exit profiling

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Message-ID: <CAN86XOZdW7aZXhSU2=gP5TrRQc8wLmtTQui0J2kwhchp2pnbeQ@mail.gmail.com>
Date:   Mon, 16 May 2022 21:30:00 +0200
From:   Wei Zhang <zhanwei@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Suleiman Souhlal <suleiman@...gle.com>
Cc:     Sangwhan Moon <sxm@...gle.com>, Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jing Zhang <jingzhangos@...gle.com>,
        David Matlack <dmatlack@...gle.com>
Subject: Re: [PATCH 0/2] KVM: x86: Fix incorrect VM-exit profiling

> 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.