linux-kernel - [PATCH] x86: Fix static_key in load_mm

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Date:	Thu, 9 Jul 2015 19:23:38 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mikulas Patocka <mpatocka@...hat.com>,
	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Vince Weaver <vince@...ter.net>,
	"hillf.zj" <hillf.zj@...baba-inc.com>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] x86: Fix static_key in load_mm_cr4()


Mikulas reported his K6-3 not booting. This is because the static_key
confusion struck and bit Andy, this wants to be static_key_false().

Fixes: a66734297f78 ("perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks")
Cc: Andy Lutomirski <luto@...capital.net>
Reported-by: Mikulas Patocka <mpatocka@...hat.com>
Tested-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/mmu_context.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 5e8daee7c5c9..804a3a6030ca 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -23,7 +23,7 @@ extern struct static_key rdpmc_always_available;
 
 static inline void load_mm_cr4(struct mm_struct *mm)
 {
-	if (static_key_true(&rdpmc_always_available) ||
+	if (static_key_false(&rdpmc_always_available) ||
 	    atomic_read(&mm->context.perf_rdpmc_allowed))
 		cr4_set_bits(X86_CR4_PCE);
 	else
--
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