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From: Thomas Gleixner <tglx@linutronix.de>
To: David Woodhouse <dwmw2@infradead.org>
Cc: karahmed@amazon.de, x86@kernel.org, kvm@vger.kernel.org,
	torvalds@linux-foundation.org, pbonzini@redhat.com,
	linux-kernel@vger.kernel.org, bp@alien8.de, peterz@infradead.org,
	jmattson@google.com, rkrcmar@redhat.com,
	arjan.van.de.ven@intel.com, dave.hansen@intel.com,
	mingo@kernel.org
Subject: Re: [PATCH v3 2/4] x86/speculation: Support "Enhanced IBRS" on future CPUs
Date: Mon, 26 Feb 2018 20:55:05 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.21.1802262054160.1402@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1519125725.7876.117.camel@infradead.org>

[-- Attachment #1: Type: text/plain, Size: 834 bytes --]

On Tue, 20 Feb 2018, David Woodhouse wrote:
> On Tue, 2018-02-20 at 11:42 +0100, Thomas Gleixner wrote:
> > 
> > > > However, Paolo is very insistent that taking the trap every time is
> > > > actually a lot *slower* than really frobbing IBRS on certain
> > > > microarchitectures, so my hand-waving "pfft, what did they expect?" is
> > > > not acceptable.
> > > > 
> > > > Which I think puts us back to the "throwing the toys out of the pram"
> > 
> > There are no more toys in the pram. I threw them all out weeks ago ...
> 
> One option is to take the patch as-is¹ with the trap on every access.
> As soon as Intel define that 'IBRS_ALL_AND_THE_BIT_IS_A_NOOP' bit in
> MSR_IA32_ARCH_CAPABILITIES, *then* we can expose it to guests directly
> again just as we do at the moment.

Arjan, is there any update on this?

Thanks,

	tglx

  parent reply	other threads:[~2018-02-26 19:55 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-19 10:50 [PATCH v3 0/4] Speculation control improvements David Woodhouse
2018-02-19 10:50 ` [PATCH v3 1/4] x86/speculation: Use IBRS if available before calling into firmware David Woodhouse
2018-02-20  7:44   ` Thomas Gleixner
2018-02-20 10:29   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-02-19 10:50 ` [PATCH v3 2/4] x86/speculation: Support "Enhanced IBRS" on future CPUs David Woodhouse
2018-02-20  8:31   ` Thomas Gleixner
2018-02-20  8:53     ` David Woodhouse
2018-02-20 10:37       ` Thomas Gleixner
2018-02-20 10:42         ` Thomas Gleixner
2018-02-20 11:22           ` David Woodhouse
2018-02-20 11:28             ` Paolo Bonzini
2018-02-26 19:55             ` Thomas Gleixner [this message]
2018-02-20 11:26   ` Paolo Bonzini
2018-02-19 10:50 ` [PATCH v3 3/4] Revert "x86/retpoline: Simplify vmexit_fill_RSB()" David Woodhouse
2018-02-20  8:35   ` Thomas Gleixner
2018-02-20 10:28   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-02-19 10:50 ` [PATCH v3 4/4] x86/retpoline: Support retpoline build with Clang David Woodhouse
2018-02-20  8:36   ` Thomas Gleixner
2018-02-20  8:45     ` David Woodhouse
2018-02-20 10:29   ` [tip:x86/pti] x86/retpoline: Support retpoline builds " tip-bot for David Woodhouse

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