linux-kernel - Re: [PATCH v2 1/3] KVM: x86: add support for user wait instructions

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Message-ID: <20190527103003.GX2623@hirez.programming.kicks-ass.net>
Date:   Mon, 27 May 2019 12:30:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tao Xu <tao3.xu@...el.com>
Cc:     pbonzini@...hat.com, rkrcmar@...hat.com, corbet@....net,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        sean.j.christopherson@...el.com, x86@...nel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, jingqi.liu@...el.com
Subject: Re: [PATCH v2 1/3] KVM: x86: add support for user wait instructions

On Fri, May 24, 2019 at 03:56:35PM +0800, Tao Xu wrote:
> This patch adds support for UMONITOR, UMWAIT and TPAUSE instructions
> in kvm, and by default dont't expose it to kvm and provide a capability
> to enable it.

I'm thinking this should be conditional on the guest being a 1:1 guest,
and I also seem to remember we have bits for that already -- they were
used to disable paravirt spinlocks for example.