linux-kernel - [PATCH 1/3] x86/init: Fix cr4_init

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Date:   Wed, 28 Sep 2016 12:34:14 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     david@...giorato.net, Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>, stable@...r.kernel.org
Subject: [PATCH 1/3] 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().

Cc: stable@...r.kernel.org
Reported-by: david@...giorato.net
Fixes: 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4")
Signed-off-by: Andy Lutomirski <luto@...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 6fa85944af83..dee8a70382ba 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. */
-- 
2.7.4