[tip: ras/core] x86/mce/inject: Only write MCA_MISC when a value has been supplied

[tip-bot2 for Yazen Ghannam]

The following commit has been merged into the ras/core branch of tip:

Commit-ID:     ede18982f19942c7333530cf4fbf271e318df1b2
Gitweb:        https://git.kernel.org/tip/ede18982f19942c7333530cf4fbf271e318df1b2
Author:        Yazen Ghannam <yazen.ghannam@xxxxxxx>
AuthorDate:    Thu, 23 May 2024 10:56:33 -05:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Mon, 27 May 2024 10:42:35 +02:00

x86/mce/inject: Only write MCA_MISC when a value has been supplied

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>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240523155641.2805411-2-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 94953d7..8d18074 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);
 	}
 }