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

From Paul Gortmaker <paul.gortmaker@windriver.com>
Newsgroups linux.kernel
Subject Re: runtime regression with "x86/mm/pat: Emulate PAT when it is disabled"
Date 2016-03-10 20:10 +0100
Message-ID <rbe8a-2SM-17@gated-at.bofh.it> (permalink)
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[Re: runtime regression with "x86/mm/pat: Emulate PAT when it is disabled"] On 10/03/2016 (Thu 18:20) Borislav Petkov wrote:

> On Thu, Mar 10, 2016 at 09:49:51AM -0700, Toshi Kani wrote:
> > This confirms the issue - QEMU's virtual Intel CPU does not support MTRR. 
> > 
> > When MTRR is disabled, the kernel does not call pat_init().  pat_enabled()
> > is still set to true when CONFIG_X86_PAT is set.  CONFIG_X86_PAT depends on
> > CONFIG_MTRR, and assumes that MTRR is enabled. 
> 
> Aha, so "qemu32" model doesn't support MTRRs but "kvm32" does, for
> example. And so do the majority of the other CPU types.

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?

> 
> Paul, can you guys run with something else besides "qemu32"? You can
> even take a 64-bit one and run a 32-bit guest on it.

That is probably more of an RP question.  In principle I guess other CPU
types are on the table, and most likely qemu32 is just there from
historical reasons.  We do know that we don't want "-cpu host" though,
since that will introduce variability into the automated testing.

Paul.
--

> 
> :-)
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
> --

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Thread

Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paul Gortmaker <paul.gortmaker@windriver.com> - 2016-03-04 19:40 +0100
  Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-04 22:30 +0100
    Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paul Gortmaker <paul.gortmaker@windriver.com> - 2016-03-07 01:40 +0100
      Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-07 16:20 +0100
        Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-07 23:50 +0100
          Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paul Gortmaker <paul.gortmaker@windriver.com> - 2016-03-08 01:00 +0100
            Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-08 01:10 +0100
              Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-08 01:50 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paul Gortmaker <paul.gortmaker@windriver.com> - 2016-03-08 04:30 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-08 16:50 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paul Gortmaker <paul.gortmaker@windriver.com> - 2016-03-10 15:50 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-10 17:00 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Borislav Petkov <bp@suse.de> - 2016-03-10 18:30 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paul Gortmaker <paul.gortmaker@windriver.com> - 2016-03-10 20:10 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-10 20:20 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Borislav Petkov <bp@suse.de> - 2016-03-10 20:30 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-03-11 14:30 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Borislav Petkov <bp@suse.de> - 2016-03-11 14:50 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paolo Bonzini <pbonzini@redhat.com> - 2016-03-11 20:20 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Borislav Petkov <bp@suse.de> - 2016-03-11 23:20 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Bruce Ashfield <bruce.ashfield@windriver.com> - 2016-03-11 23:30 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Richard Purdie <richard.purdie@linuxfoundation.org> - 2016-03-12 00:50 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Borislav Petkov <bp@suse.de> - 2016-03-12 13:10 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-10 20:20 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Borislav Petkov <bp@suse.de> - 2016-03-10 20:30 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-10 20:40 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Borislav Petkov <bp@suse.de> - 2016-03-10 22:10 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-10 23:30 +0100
              Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paul Gortmaker <paul.gortmaker@windriver.com> - 2016-03-08 04:20 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-08 16:30 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Toshi Kani <toshi.kani@hpe.com> - 2016-03-08 17:10 +0100
                Re: runtime regression with "x86/mm/pat: Emulate PAT when it is  disabled" Paul Gortmaker <paul.gortmaker@windriver.com> - 2016-03-08 17:10 +0100

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