Re: [PATCH v3 08/10] x86/setcpuid: Add kernel option setcpuid
From: Fenghua Yu
Date: Mon Feb 04 2019 - 16:15:27 EST
On Mon, Feb 04, 2019 at 11:05:52AM -0800, Dave Hansen wrote:
> On 2/4/19 9:49 AM, Thomas Gleixner wrote:
> > On Fri, 1 Feb 2019, Fenghua Yu wrote:
> >> This option behaves like existing kernel option clearcpuid.
> > No it does NOT. clearcpuid allows to disable things.
> > This allows to enable random CPUID bits without any sanity checking. Not
> > going to happen. We made it clear in the past that functionality needs to
> > be detectable by enumeration. We do quirks for broken crap, but this is
> > just not how it works.
> Hi Thomas,
> I think we are trying persuade you like mentioned here:
> > http://lkml.kernel.org/r/alpine.DEB.2.21.1807122153170.1597@xxxxxxxxxxxxxxxxxxxxxxx
> But, we're not being very persuasive because we kinda forgot about the
> "if and only if" condition that you mentioned.
Intel SDM published TODAY does have IA32_CORE_CAPABILITY MSR enumerateion
bit CPUID.0x7.0:EDX now. Please check today's SDM for the bit:
I will add the two patches that enumerate the MSR and #AC for split lock
in the next version.