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x86/msr: Set the return value to zero when native_rdmsr_safe() fails 

This will cause unchecked native_rdmsr_safe() failures to return
deterministic results.

Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/515fb611449a755312a476cfe11675906e7ddf6c.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2016-04-02 07:01:40 -07:00 committed by Ingo Molnar
parent 4985ce15a3
commit b828b79fcc
1 changed files with 4 additions and 1 deletions
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5
arch/x86/include/asm/msr.h
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@ -101,7 +101,10 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
asm volatile("2: rdmsr ; xor %[err],%[err]\n" asm volatile("2: rdmsr ; xor %[err],%[err]\n"
"1:\n\t" "1:\n\t"
".section .fixup,\"ax\"\n\t" ".section .fixup,\"ax\"\n\t"
"3: mov %[fault],%[err] ; jmp 1b\n\t" "3: mov %[fault],%[err]\n\t"
"xorl %%eax, %%eax\n\t"
"xorl %%edx, %%edx\n\t"
"jmp 1b\n\t"
".previous\n\t" ".previous\n\t"
_ASM_EXTABLE(2b, 3b) _ASM_EXTABLE(2b, 3b)
: [err] "=r" (*err), EAX_EDX_RET(val, low, high) : [err] "=r" (*err), EAX_EDX_RET(val, low, high)