From c08d517480ea342cc43acdacc5cf4a795e18151d Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@kernel.org>
Date: Thu, 1 Jun 2017 15:52:23 +0200
Subject: [PATCH] Revert "x86/PAT: Fix Xorg regression on CPUs that don't
support PAT"
This reverts commit cbed27cdf0e3f7ea3b2259e86b9e34df02be3fe4.
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>
---
arch/x86/mm/pat.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 83a59a67757a..9b78685b66e6 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -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;
}
--
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