From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
jmattson@google.com, stable@vger.kernel.org
Subject: Re: [PATCH v2] KVM: x86: Allow guests to see MSR_IA32_TSX_CTRL even if tsx=off
Date: Mon, 1 Feb 2021 08:38:24 -0800 [thread overview]
Message-ID: <YBgugM03fsEiOxz1@google.com> (raw)
In-Reply-To: <618c5513-5092-f7cd-b47b-933936001180@redhat.com>
On Mon, Feb 01, 2021, Paolo Bonzini wrote:
> On 01/02/21 09:46, Paolo Bonzini wrote:
> > >
> > > This comment be updated to call out the new TSX_CTRL behavior.
> > >
> > > /*
> > > * On TAA affected systems:
> > > * - nothing to do if TSX is disabled on the host.
> > > * - we emulate TSX_CTRL if present on the host.
> > > * This lets the guest use VERW to clear CPU buffers.
> > > */
> >
> > Ok.
>
> Hmm, but the comment is even more accurate now than before, isn't it? It
> said nothing about hiding TSX_CTRL, so now it matches the code below.
Ha, that is technically true. But it says "nothing to do..." and then clears a
flag. The other interpretation of "nothing to do... at runtime" is also wrong
as KVM emulates the MSR as a nop.
I guess I just find the whole comment more confusing than the code itself.
next prev parent reply other threads:[~2021-02-01 16:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-29 10:19 [PATCH v2] KVM: x86: Allow guests to see MSR_IA32_TSX_CTRL even if tsx=off Paolo Bonzini
2021-01-29 16:58 ` Sean Christopherson
2021-02-01 8:46 ` Paolo Bonzini
2021-02-01 9:08 ` Paolo Bonzini
2021-02-01 16:38 ` Sean Christopherson [this message]
2021-02-01 17:34 ` Paolo Bonzini
2021-02-01 17:36 ` Sean Christopherson
2021-02-01 17:03 ` Sean Christopherson
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