linux-kernel - Re: runtime regression with "x86/mm/pat: Emulate PAT when it is disabled"

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Date:	Thu, 10 Mar 2016 13:24:11 -0700
From:	Toshi Kani <toshi.kani@....com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Richard Purdie <richard.purdie@...uxfoundation.org>,
	Toshi Kani <toshi.kani@...com>,
	Bruce Ashfield <bruce.ashfield@...driver.com>,
	"Hart, Darren" <darren.hart@...el.com>,
	"saul.wold" <saul.wold@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: runtime regression with "x86/mm/pat: Emulate PAT when it is
 disabled"

On Thu, 2016-03-10 at 20:20 +0100, Borislav Petkov wrote:
> On Thu, Mar 10, 2016 at 01:04:21PM -0700, Toshi Kani wrote:
> > I will send a patch that sets PAT disabled when MTRR is disabled.  This
> > will solve the Paul's issue.  His qemu32 model does not support PAT,
> > either.
> 
> It does, see my other mail. We need to figure out first why is
> pat_init() being called as part of MTRR setup.

I am not familiar with PPRO_FEATURES, but shouldn't 'flags' in
/proc/cpuinfo show "pat" when X86_FEATURE_PAT is set?

pat_init() is being called as part of MTRR setup because PAT initialization
requires the same CPU rendezvous operation implemented in the MTRR code.

Thanks,
-Toshi