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

David Woodhouse
2018-02-19T09:29:39Z

[-- Attachment #1: Type: text/plain, Size: 683 bytes --]

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_id       : GenuineIntel
> cpu family      : 6
> model           : 62
> model name      : Intel(R) Xeon(R) CPU E5-2680 v2 @ 2.80GHz
> stepping        : 4
> microcode       : 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?

[-- Attachment #2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 5213 bytes --]