linux-kernel - [tip:x86/urgent] x86/init: Fix cr4_init

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Message-ID: <tip-e1bfc11c5a6f40222a698a818dc269113245820e@git.kernel.org>
Date:   Thu, 29 Sep 2016 11:21:42 -0700
From:   tip-bot for Andy Lutomirski <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, jpoimboe@...hat.com,
        peterz@...radead.org, tglx@...utronix.de,
        torvalds@...ux-foundation.org, bp@...e.de, dvlasenk@...hat.com,
        brgerst@...il.com, hpa@...or.com, bp@...en8.de, mingo@...nel.org,
        luto@...nel.org
Subject: [tip:x86/urgent] x86/init: Fix cr4_init_shadow() on CR4-less
 machines

Commit-ID:  e1bfc11c5a6f40222a698a818dc269113245820e
Gitweb:     http://git.kernel.org/tip/e1bfc11c5a6f40222a698a818dc269113245820e
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Wed, 28 Sep 2016 12:34:14 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 29 Sep 2016 19:08:30 +0200

x86/init: Fix cr4_init_shadow() on CR4-less machines

cr4_init_shadow() will panic on 486-like machines without CR4.  Fix
it using __read_cr4_safe().

Reported-by: david@...giorato.net
Signed-off-by: Andy Lutomirski <luto@...nel.org>
Reviewed-by: Borislav Petkov <bp@...e.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org
Fixes: 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4")
Link: http://lkml.kernel.org/r/43a20f81fb504013bf613913dc25574b45336a61.1475091074.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/tlbflush.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 6fa8594..dee8a70 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -81,7 +81,7 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate);
 /* Initialize cr4 shadow for this CPU. */
 static inline void cr4_init_shadow(void)
 {
-	this_cpu_write(cpu_tlbstate.cr4, __read_cr4());
+	this_cpu_write(cpu_tlbstate.cr4, __read_cr4_safe());
 }
 
 /* Set in this cpu's CR4. */