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

c08d5174 · Ingo Molnar <[email protected]> · 2017-06-01 15:52:23 +02:00

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 <[email protected]>
Reported-by: Chris Wilson <[email protected]>
Acked-by: Andy Lutomirski <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Luis R. Rodriguez <[email protected]>
Cc: Mikulas Patocka <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: [email protected] # v4.2+
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Commit: c08d517480ea342cc43acdacc5cf4a795e18151d
Parents: 5d9070b1

Changes

1 files changed · +3 −6

File	Status	Add	Del	Content
arch/x86/mm/pat.c	modified	+3	−6	View file

arch/x86/mm/pat.c

View file

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 83a59a6..9b78685 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;
 	}