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Revert "x86/PAT: Fix Xorg regression on CPUs that don't support PAT" 

This reverts commit cbed27cdf0.

As Andy Lutomirski observed:

 "I think this patch is bogus. pat_enabled() sure looks like it's
  supposed to return true if PAT is *enabled*, and these days PAT is
  'enabled' even if there's no HW PAT support."

Reported-by: Bernhard Held <berny156@gmx.de>
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: stable@vger.kernel.org # v4.2+
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2017-06-01 15:52:23 +02:00
parent 5d9070b1f0
commit c08d517480
1 changed files with 3 additions and 6 deletions
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9
arch/x86/mm/pat.c
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@ -65,11 +65,9 @@ static int __init nopat(char *str)
}
early_param("nopat", nopat);
static bool __read_mostly __pat_initialized = false;
bool pat_enabled(void)
{
return __pat_initialized;
return !!__pat_enabled;
}
EXPORT_SYMBOL_GPL(pat_enabled);
@ -227,14 +225,13 @@ static void pat_bsp_init(u64 pat)
}
wrmsrl(MSR_IA32_CR_PAT, pat);
__pat_initialized = true;
__init_cache_modes(pat);
}
static void pat_ap_init(u64 pat)
{
if (!this_cpu_has(X86_FEATURE_PAT)) {
if (!boot_cpu_has(X86_FEATURE_PAT)) {
/*
* If this happens we are on a secondary CPU, but switched to
* PAT on the boot CPU. We have no way to undo PAT.
@ -309,7 +306,7 @@ void pat_init(void)
u64 pat;
struct cpuinfo_x86 *c = &boot_cpu_data;
if (!__pat_enabled) {
if (!pat_enabled()) {
init_cache_modes();
return;
}