x86/CPU/AMD: Simplify the spectral chicken fix

msr_set_bit() takes a bit number to set but MSR_ZEN2_SPECTRAL_CHICKEN_BIT
is a bit mask. The usual pattern that code uses is a _BIT-named type
macro instead of a mask.

So convert it to a bit number to reflect that.

Also, msr_set_bit() already does the reading and checking whether the
bit needs to be set so use that instead of a local variable.

Fixup tabbing while at it.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://patch.msgid.link/20251230110731.28108-1-bp@kernel.org

Author: bp3tk0v

arch/x86/include/asm/msr-index.h

@@ -794,8 +794,8 @@
 #define MSR_F19H_UMC_PERF_CTR           0xc0010801
 
 /* Zen 2 */
-#define MSR_ZEN2_SPECTRAL_CHICKEN       0xc00110e3
-#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT   BIT_ULL(1)
+#define MSR_ZEN2_SPECTRAL_CHICKEN	0xc00110e3
+#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT	1
 
 /* Fam 17h MSRs */
 #define MSR_F17H_IRPERF			0xc00000e9

arch/x86/kernel/cpu/amd.c

@@ -900,20 +900,14 @@ static void fix_erratum_1386(struct cpuinfo_x86 *c)
 void init_spectral_chicken(struct cpuinfo_x86 *c)
 {
 #ifdef CONFIG_MITIGATION_UNRET_ENTRY
-	u64 value;
-
 	/*
 	 * On Zen2 we offer this chicken (bit) on the altar of Speculation.
 	 *
 	 * This suppresses speculation from the middle of a basic block, i.e. it
 	 * suppresses non-branch predictions.
 	 */
-	if (!cpu_has(c, X86_FEATURE_HYPERVISOR)) {
-		if (!rdmsrq_safe(MSR_ZEN2_SPECTRAL_CHICKEN, &value)) {
-			value |= MSR_ZEN2_SPECTRAL_CHICKEN_BIT;
-			wrmsrq_safe(MSR_ZEN2_SPECTRAL_CHICKEN, value);
-		}
-	}
+	if (!cpu_has(c, X86_FEATURE_HYPERVISOR))
+		msr_set_bit(MSR_ZEN2_SPECTRAL_CHICKEN, MSR_ZEN2_SPECTRAL_CHICKEN_BIT);
 #endif
 }
 

tools/arch/x86/include/asm/msr-index.h

@@ -770,8 +770,8 @@
 #define MSR_F19H_UMC_PERF_CTR           0xc0010801
 
 /* Zen 2 */
-#define MSR_ZEN2_SPECTRAL_CHICKEN       0xc00110e3
-#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT   BIT_ULL(1)
+#define MSR_ZEN2_SPECTRAL_CHICKEN	0xc00110e3
+#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT	1
 
 /* Fam 17h MSRs */
 #define MSR_F17H_IRPERF			0xc00000e9