From 6c0db7437f4d0a0ce9dcbecb811275d034b11b96 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 28 Sep 2016 12:34:14 -0700 Subject: [PATCH] x86/init: Fix cr4_init_shadow() on CR4-less machines commit e1bfc11c5a6f40222a698a818dc269113245820e upstream. cr4_init_shadow() will panic on 486-like machines without CR4. Fix it using __read_cr4_safe(). Reported-by: david@saggiorato.net Signed-off-by: Andy Lutomirski Reviewed-by: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner 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 Signed-off-by: Greg Kroah-Hartman --- 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 3142218e546f..6433e28dc9c8 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -32,7 +32,7 @@ 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. */ -- 2.34.1