[coreboot-gerrit] Change in coreboot[master]: cpu/x86/msr: introduce helpers msr_read, msr_write

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/52548 )

Change subject: cpu/x86/msr: introduce helpers msr_read, msr_write
......................................................................

cpu/x86/msr: introduce helpers msr_read, msr_write

The existing helpers for reading/writing MSRs (rdmsr, wrmsr) require use
of the struct `msr_t`, which splits the MSR value into two 32 bit parts.
In many cases, where simple 32 bit or 64 bit values are written, this
bloats the code by unnecessarly having to use that struct.

Thus, introduce the helpers `msr_read` and `msr_write`, which take or
return `uint64_t` values, so the code condenses to a single line or two,
without having to deal with `msr_t`.

Example 1:

~~~
msr_t msr = {
  .lo = read32((void *)(uintptr_t)0xfed30880),
  .hi = 0,
};

msr.lo |= 1;
wrmsr(0x123, msr);
~~~

becomes

~~~
uint32_t foo = read32((void *)(uintptr_t)0xfed30880);
msr_write(0x123, foo | 1)
~~~

Example 2:

~~~
msr_t msr = rdmsr(0xff);
uint64_t msr_val = (msr.hi << 32) | msr.lo;
~~~

becomes

~~~
uint64_t msr_val = msr_read(0xff);
~~~

Change-Id: I27333a4bdfe3c8cebfe49a16a4f1a066f558c4ce
Signed-off-by: Michael Niewöhner 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52548
Reviewed-by: Nico Huber 
Reviewed-by: Felix Held 
Reviewed-by: Tim Wawrzynczak 
Tested-by: build bot (Jenkins) 
---
M src/include/cpu/x86/msr.h
1 file changed, 26 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Nico Huber: Looks good to me, approved
  Felix Held: Looks good to me, but someone else must approve
  Tim Wawrzynczak: Looks good to me, but someone else must approve

diff --git a/src/include/cpu/x86/msr.h b/src/include/cpu/x86/msr.h
index 5ae3ddf..bc367d7 100644
--- a/src/include/cpu/x86/msr.h
+++ b/src/include/cpu/x86/msr.h
@@ -301,6 +301,32 @@
 }

/**
+ * Helper for reading a MSR
+ *
+ * @param[in] reg	The MSR.
+ */
+static inline uint64_t msr_read(unsigned int reg)
+{
+	msr_t msr = rdmsr(reg);
+	return (((uint64_t)msr.hi << 32) | msr.lo);
+}
+
+/**
+ * Helper for writing a MSR
+ *
+ * @param[in] reg	The MSR.
+ * @param[in] value	The value to be written to the MSR.
+ */
+static inline void msr_write(unsigned int reg, uint64_t value)
+{
+	msr_t msr = {
+		.lo = (unsigned int)value,
+		.hi = (unsigned int)(value >> 32)
+	};
+	wrmsr(reg, msr);
+}
+
+/**
  * Helper for (un)setting MSR bitmasks
  *
  * @param[in] reg	The MSR.