Date: Thu, 10 Mar 2016 20:19:33 +0100
From: Borislav Petkov <bp@suse.de>
To: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Toshi Kani <toshi.kani@hpe.com>,
        Richard Purdie <richard.purdie@linuxfoundation.org>,
        Toshi Kani <toshi.kani@hp.com>,
        Bruce Ashfield <bruce.ashfield@windriver.com>,
        "Hart, Darren" <darren.hart@intel.com>,
        "saul.wold" <saul.wold@intel.com>, linux-kernel@vger.kernel.org
Subject: Re: runtime regression with "x86/mm/pat: Emulate PAT when it is
 disabled"
Message-ID: <20160310191933.GC2194@pd.tnic>
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On Thu, Mar 10, 2016 at 02:04:29PM -0500, Paul Gortmaker wrote:
> So, I guess that is a qemu bug?  If there is no real silicon out there
> that has no MTRR but does claim PAT, then qemu32 is a flawed CPU type?

Well, AFAICT, "qemu32" is emulating something PPRO-like:

#define PPRO_FEATURES (CPUID_FP87 | CPUID_DE | CPUID_PSE | CPUID_TSC | \
          CPUID_MSR | CPUID_MCE | CPUID_CX8 | CPUID_PGE | CPUID_CMOV | \
          CPUID_PAT | CPUID_FXSR | CPUID_MMX | CPUID_SSE | CPUID_SSE2 | \
	  ^^^^^^^^^

and that one advertizes PAT but not MTRRs.

I need to go dig into history to find out what PPRO actually supported.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--