From c08d517480ea342cc43acdacc5cf4a795e18151d Mon Sep 17 00:00:00 2001 From: Ingo Molnar 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 Reported-by: Chris Wilson Acked-by: Andy Lutomirski Cc: Andrew Morton Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Mikulas Patocka Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Cc: stable@vger.kernel.org # v4.2+ Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- 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; } -- GitLab