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Date:   Sun, 21 Jan 2018 20:04:30 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     David Woodhouse <dwmw2@infradead.org>
Cc:     arjan@linux.intel.com, tglx@linutronix.de, karahmed@amazon.de,
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        torvalds@linux-foundation.org, gregkh@linux-foundation.org
Subject: Re: [PATCH v2 5/8] x86/speculation: Add basic support for IBPB
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On Sun, Jan 21, 2018 at 06:54:22PM +0000, David Woodhouse wrote:
> Because we're backporting this to every stable kernel under the sun,
> and they don't already require asm-goto.

Considering the cost of the barrier, I'd simplify the whole endeavor
*considerably* for backporting:

	if (boot_cpu_has(X86_FEATURE_IBPB))
		wrmsr(MSR_IA32_PRED_CMD, PRED_CMD_IBPB, 0);

Problem solved.

Upstream can then do static_cpu_has() if it wants to.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.