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Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table

From Toshi Kani <toshi.kani@hpe.com>
Newsgroups linux.kernel
Subject Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table
Date 2016-03-14 21:50 +0100
Message-ID <rcHB8-pu-13@gated-at.bofh.it> (permalink)
References (2 earlier) <rbroJ-3VO-11@gated-at.bofh.it> <rbxkt-8dl-7@gated-at.bofh.it> <rbxDP-8op-1@gated-at.bofh.it> <rbA8G-1R9-35@gated-at.bofh.it> <rbQn8-5qL-13@gated-at.bofh.it>
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On Sat, 2016-03-12 at 12:55 +0100, Borislav Petkov wrote:
> Ok, let's start again.
> 
> So what's wrong with this simpler, cleaner version below?
> 
> * It makes sure to run the rendezvous handler on the BP on init.
> 
> * It disables PAT otherwise.
> 
> * Oh, and it boots fine with Paul's reproducer, X is there (even though
> vncviewer dies when X starts with "Rect too large: 640x480 at (0, 0)"
> and I have to reconnect to see the X window).
> 
> In dmesg I see "x86/PAT: Disabled by MTRR".

Your patch is a simplified version of mine.  So, yes, it fixes the Paul's
issue, but it does not address other issues that my patchset also
addressed.  In specific, I think your patch has the following issues.

- pat_disable() is now callable from other modules. So, it needs to check
with boot_cpu_done. We cannot disable PAT once it is initialized.

- mtrr_bp_init() needs to check with mtrr_enabled() when it
calls mtrr_pat_setup_bp(). Otherwise, PAT is left initialized on BSP only
when MTRR is disabled by its MSR. In your patch, mtrr_bp_init() calls
pat_setup() again, but it does not help since boot_cpu_done is set.

- When PAT is disabled in CPU feature, pat_bsp_init() calls pat_disable()
and returns. However, it does not initialize a PAT table by calling
pat_init_cache_modes().

- When CONFIG_MTRR is unset, it does not call pat_setup().

Thanks,
-Toshi

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Thread

[PATCH 0/2] Refactor MTRR and PAT initializations Toshi Kani <toshi.kani@hpe.com> - 2016-03-11 05:00 +0100
  [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Toshi Kani <toshi.kani@hpe.com> - 2016-03-11 05:00 +0100
    Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Borislav Petkov <bp@alien8.de> - 2016-03-11 10:20 +0100
      Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT  table Toshi Kani <toshi.kani@hpe.com> - 2016-03-11 16:40 +0100
        Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Borislav Petkov <bp@alien8.de> - 2016-03-11 17:00 +0100
          Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT  table Toshi Kani <toshi.kani@hpe.com> - 2016-03-11 19:40 +0100
            Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Borislav Petkov <bp@alien8.de> - 2016-03-12 13:00 +0100
              Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT  table Toshi Kani <toshi.kani@hpe.com> - 2016-03-14 21:50 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Borislav Petkov <bp@alien8.de> - 2016-03-15 12:10 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT  table Toshi Kani <toshi.kani@hpe.com> - 2016-03-15 22:10 +0100
              Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-03-15 01:30 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT  table Toshi Kani <toshi.kani@hpe.com> - 2016-03-15 03:20 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Borislav Petkov <bp@alien8.de> - 2016-03-15 12:10 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT  table Toshi Kani <toshi.kani@hpe.com> - 2016-03-15 16:00 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Borislav Petkov <bp@alien8.de> - 2016-03-15 16:50 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT  table Toshi Kani <toshi.kani@hpe.com> - 2016-03-15 17:20 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table Borislav Petkov <bp@alien8.de> - 2016-03-15 17:40 +0100
                Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-03-15 22:40 +0100
  [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Toshi Kani <toshi.kani@hpe.com> - 2016-03-11 05:00 +0100
    Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Ingo Molnar <mingo@kernel.org> - 2016-03-11 10:10 +0100
      Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Ingo Molnar <mingo@kernel.org> - 2016-03-11 10:20 +0100
        Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Toshi Kani <toshi.kani@hpe.com> - 2016-03-11 18:50 +0100
          Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Ingo Molnar <mingo@kernel.org> - 2016-03-12 17:20 +0100
            Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Toshi Kani <toshi.kani@hpe.com> - 2016-03-14 20:00 +0100
          Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code "Luis R. Rodriguez" <mcgrof@suse.com> - 2016-03-15 00:00 +0100
            Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Toshi Kani <toshi.kani@hpe.com> - 2016-03-15 00:50 +0100
              Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Borislav Petkov <bp@suse.de> - 2016-03-15 17:00 +0100
    Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Borislav Petkov <bp@alien8.de> - 2016-03-11 10:30 +0100
      Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Toshi Kani <toshi.kani@hpe.com> - 2016-03-11 19:10 +0100
        Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-03-11 23:20 +0100
          Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Toshi Kani <toshi.kani@hpe.com> - 2016-03-12 00:10 +0100
            Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-03-12 00:40 +0100
              Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Toshi Kani <toshi.kani@hpe.com> - 2016-03-12 01:30 +0100
                Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-03-15 01:20 +0100
                Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code Toshi Kani <toshi.kani@hpe.com> - 2016-03-16 00:00 +0100
                Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-03-16 00:30 +0100

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