include/cpu/msr.h: transform into an union

This makes it easier to get the content of an msr into a full 64bit
variable.

Change-Id: I1b026cd3807fd68d805051a74b3d31fcde1c5626
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68572
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

2 files changed, 11 insertions, 12 deletions

diff --git a/src/include/cpu/x86/msr.h b/src/include/cpu/x86/msr.h
index f4e39859cf..33eb457f1a 100644
--- a/src/include/cpu/x86/msr.h
+++ b/src/include/cpu/x86/msr.h
@@ -285,7 +285,7 @@ static inline enum mca_err_code_types mca_err_type(msr_t reg)
 static inline uint64_t msr_read(unsigned int reg)
 {
 	msr_t msr = rdmsr(reg);
-	return (((uint64_t)msr.hi << 32) | msr.lo);
+	return msr.raw;
 }
 
 /**
@@ -296,10 +296,7 @@ static inline uint64_t msr_read(unsigned int reg)
  */
 static inline void msr_write(unsigned int reg, uint64_t value)
 {
-	msr_t msr = {
-		.lo = (unsigned int)value,
-		.hi = (unsigned int)(value >> 32)
-	};
+	msr_t msr = { .raw = value };
 	wrmsr(reg, msr);
 }
 
@@ -315,10 +312,8 @@ static inline void msr_unset_and_set(unsigned int reg, uint64_t unset, uint64_t
 	msr_t msr;
 
 	msr = rdmsr(reg);
-	msr.lo &= (unsigned int)~unset;
-	msr.hi &= (unsigned int)~(unset >> 32);
-	msr.lo |= (unsigned int)set;
-	msr.hi |= (unsigned int)(set >> 32);
+	msr.raw &= ~unset;
+	msr.raw |= set;
 	wrmsr(reg, msr);
 }
 
diff --git a/src/include/cpu/x86/msr_access.h b/src/include/cpu/x86/msr_access.h
index a7f72fd077..33029cc653 100644
--- a/src/include/cpu/x86/msr_access.h
+++ b/src/include/cpu/x86/msr_access.h
@@ -6,10 +6,14 @@
 #ifndef __ASSEMBLER__
 #include <types.h>
 
-typedef struct msr_struct {
-	unsigned int lo;
-	unsigned int hi;
+typedef union msr_union {
+	struct {
+		unsigned int lo;
+		unsigned int hi;
+	};
+	uint64_t raw;
 } msr_t;
+_Static_assert(sizeof(msr_t) == sizeof(uint64_t), "Incorrect size for msr_t");
 
 #if CONFIG(SOC_SETS_MSRS)
 msr_t soc_msr_read(unsigned int index);