Re: [tip:x86/pti] x86/speculation: Use IBRS if available before calling into firmware

[David Woodhouse]

On Mon, 2018-02-19 at 10:20 +0100, Peter Zijlstra wrote:
> 
> I did not update or otherwise change packages while I was bisecting; the
> machine is:
> 
> vendor_idÂÂÂÂÂÂ : GenuineIntel
> cpu familyÂÂÂÂÂ : 6
> modelÂÂÂÂÂÂÂÂÂÂ : 62
> model nameÂÂÂÂÂ : Intel(R) Xeon(R) CPU E5-2680 v2 @ 2.80GHz
> steppingÂÂÂÂÂÂÂ : 4
> microcodeÂÂÂÂÂÂ : 0x428

That's IVX with a microcode that doesn't *have* IBRS/IBPB. I don't
think there's a publicly available microcode that does; I assume you
didn't have one and build it into your kernel for early loading, and
thus you really weren't even using IBRS here? The code never even gets
patched in?

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