From: Andy Lutomirski <luto@kernel.org>
Date: Sat, 2 Apr 2016 14:01:40 +0000 (-0700)
Subject: x86/msr: Set the return value to zero when native_rdmsr_safe() fails
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=b828b79fcced0e66492590707649dbfaea6435e6;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

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>
---

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 00050c034a13..7dc1d8fef7fd 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -101,7 +101,10 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
 	asm volatile("2: rdmsr ; xor %[err],%[err]\n"
 		     "1:\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"
 		     _ASM_EXTABLE(2b, 3b)
 		     : [err] "=r" (*err), EAX_EDX_RET(val, low, high)