From: David Woodhouse <dwmw2@infradead.org>
To: Paolo Bonzini <pbonzini@redhat.com>,
tglx@linutronix.de, x86@kernel.org, kvm@vger.kernel.org,
torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
arjan.van.de.ven@intel.com, dave.hansen@intel.com
Cc: Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 2/2] x86/speculation: Support "Enhanced IBRS" on future CPUs
Date: Fri, 16 Feb 2018 09:58:56 +0000 [thread overview]
Message-ID: <1518775136.7876.13.camel@infradead.org> (raw)
In-Reply-To: <02bd3fdd-1b73-6cab-fb09-38ba933396bd@redhat.com>
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On Tue, 2018-02-13 at 11:41 +0100, Paolo Bonzini wrote:
> On 13/02/2018 11:36, David Woodhouse wrote:
> > > > - if the VM has IBRS_ALL, pass through the MSR when it is zero and
> > > > intercept writes when it is one (no writes should happen)
> > > >
> > > > - if the VM doesn't have IBRS_ALL, do as we are doing now, independent
> > > > of what the host spectre_v2_ibrs_all() setting is.
> > >
> > > We end up having to turn IBRS on again on vmexit then, taking care that
> > > no conditional branch can go round it. So that becomes an
> > > *unconditional* wrmsr or lfence in the vmexit path. We really don't
> > > want that.
> > >
> > Note that being able to keep it simple in KVM was basically what made
> > the difference between me tolerating IBRS_ALL as Intel currently define
> > it, and throwing my toys out of the pram (as I had done in the first
> > iterations of this patch).
>
> You have my vote. :)
I was taking that as assent to the patch... could I trouble you for an
explicit ack, please?
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next prev parent reply other threads:[~2018-02-16 9:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-12 15:27 [PATCH 1/2] x86/speculation: Correct Speculation Control microcode blacklist again David Woodhouse
2018-02-12 15:27 ` [PATCH 2/2] x86/speculation: Support "Enhanced IBRS" on future CPUs David Woodhouse
2018-02-13 7:47 ` Ingo Molnar
2018-02-13 8:12 ` David Woodhouse
2018-02-13 8:02 ` Paolo Bonzini
2018-02-13 8:15 ` David Woodhouse
2018-02-13 9:58 ` Paolo Bonzini
2018-02-13 10:21 ` David Woodhouse
2018-02-13 10:36 ` David Woodhouse
2018-02-13 10:41 ` Paolo Bonzini
2018-02-13 10:53 ` David Woodhouse
2018-02-13 10:55 ` Paolo Bonzini
2018-02-16 9:58 ` David Woodhouse [this message]
2018-02-16 10:08 ` Paolo Bonzini
2018-02-16 10:21 ` David Woodhouse
2018-02-16 11:04 ` Paolo Bonzini
2018-02-16 12:10 ` David Woodhouse
2018-02-15 15:21 ` Pavel Machek
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