linux-kernel - Re: [PATCH] Move VMEnter and VMExit tracepoints closer to the actual event

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Date:   Thu, 20 May 2021 18:18:38 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Stefano De Venuto <stefano.devenuto99@...il.com>
Cc:     linux-kernel@...r.kernel.org, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, x86@...nel.org,
        hpa@...or.com, kvm@...r.kernel.org, rostedt@...dmis.org,
        y.karadz@...il.com, Dario Faggioli <dfaggioli@...e.com>
Subject: Re: [PATCH] Move VMEnter and VMExit tracepoints closer to the actual
 event

On 20/05/21 17:32, Sean Christopherson wrote:
> On VMX, I think the tracepoint can be moved below the VMWRITEs without much
> contention (though doing so is likely a nop), but moving it below
> kvm_load_guest_xsave_state() requires a bit more discussion.

Indeed; as a rule of thumb, the tracepoint on SVM could match the 
clgi/stgi region, and on VMX it could be placed in a similar location.

Paolo

> I 100% agree that the current behavior can be a bit confusing, but I wonder if
> we'd be better off "solving" that problem through documentation.