Re: [PATCH v2 5/8] x86/speculation: Add basic support for IBPB

[Borislav Petkov]

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.

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