[PATCH 1/9] x86/mce/inject: Only write MCA_MISC with user-set value

[Yazen Ghannam]

The MCA_MISC register is used to control the MCA thresholding feature on
AMD systems. Therefore, it is not generally part of the error state that
a user would adjust when testing non-thresholding cases.

However, MCA_MISC is unconditionally written even if a user does not
supply a value. The default value of '0' will be used and clobber the
register.

Write the MCA_MISC register only if the user has given a value for it.

Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
---
 arch/x86/kernel/cpu/mce/inject.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
index 94953d749475..8d18074534ff 100644
--- a/arch/x86/kernel/cpu/mce/inject.c
+++ b/arch/x86/kernel/cpu/mce/inject.c
@@ -487,12 +487,16 @@ static void prepare_msrs(void *info)
 			wrmsrl(MSR_AMD64_SMCA_MCx_ADDR(b), m.addr);
 		}
 
-		wrmsrl(MSR_AMD64_SMCA_MCx_MISC(b), m.misc);
 		wrmsrl(MSR_AMD64_SMCA_MCx_SYND(b), m.synd);
+
+		if (m.misc)
+			wrmsrl(MSR_AMD64_SMCA_MCx_MISC(b), m.misc);
 	} else {
 		wrmsrl(MSR_IA32_MCx_STATUS(b), m.status);
 		wrmsrl(MSR_IA32_MCx_ADDR(b), m.addr);
-		wrmsrl(MSR_IA32_MCx_MISC(b), m.misc);
+
+		if (m.misc)
+			wrmsrl(MSR_IA32_MCx_MISC(b), m.misc);
 	}
 }
 
-- 
2.34.1