linux-kernel - Re: [PATCH v7 10/12] KVM/x86/lbr: lazy save the guest lbr stack

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Message-ID: <20190709113942.GV3402@hirez.programming.kicks-ass.net>
Date:   Tue, 9 Jul 2019 13:39:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Wei Wang <wei.w.wang@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, pbonzini@...hat.com, kan.liang@...el.com,
        mingo@...hat.com, rkrcmar@...hat.com, like.xu@...el.com,
        jannh@...gle.com, arei.gonglei@...wei.com, jmattson@...gle.com
Subject: Re: [PATCH v7 10/12] KVM/x86/lbr: lazy save the guest lbr stack

On Mon, Jul 08, 2019 at 08:11:41AM -0700, Andi Kleen wrote:
> > I don't understand a word of that.
> > 
> > Who cares if the LBR MSRs are touched; the guest expects up-to-date
> > values when it does reads them.
> 
> This is for only when the LBRs are disabled in the guest.

But your Changelog didn't clearly state that. It was an unreadable mess.