On Wed, Apr 29, 2026 at 11:45:21AM -0700, Dave Hansen wrote:
> +/*
> + * Common paravirt and native helpers:
> + */
> +#define rdmsr(msr, low, high) \
> +do { \
> + u64 __val = paravirt_read_msr((msr)); \
> + (void)((low) = (u32)__val); \
> + (void)((high) = (u32)(__val >> 32)); \
> +} while (0)
Rather than direct all (paravirt and native) invocations of rdmsr() to
paravirt_*(), does it make sense to first introduce the common version of
helpers and direct the common version of helpers to paravirt_* or native_*?
So, we can have
+/*
+ * Common paravirt and native helpers:
+ */
+#define rdmsr(msr, low, high) \
+do { \
+ u64 __val = common_read_msr((msr)); \
+ (void)((low) = (u32)__val); \
+ (void)((high) = (u32)(__val >> 32)); \
+} while (0)
with below changes in patch 1.
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 9c2ea29e12a9..7ba5bc921526 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -171,8 +171,19 @@ static inline u64 native_read_pmc(int counter)
#ifdef CONFIG_PARAVIRT_XXL
#include <asm/paravirt.h>
+#define common_read_msr paravirt_read_msr
+#define common_read_msr_safe paravirt_read_msr_safe
+#define common_write_msr paravirt_write_msr
+#define common_write_msr_safe paravirt_write_msr_safe
#else
#include <linux/errno.h>
+
+/* Short-circuit the paravirt MSR infrastructure when it is disabled: */
+#define common_read_msr native_read_msr
+#define common_read_msr_safe native_read_msr_safe
+#define common_write_msr native_write_msr
+#define common_write_msr_safe native_write_msr_safe
+
/*
* Access to machine-specific registers (available on 586 and better only)
* Note: the rd* operations modify the parameters directly (without using
@@ -181,35 +192,35 @@ static inline u64 native_read_pmc(int counter)
#define rdmsr(msr, low, high) \
do { \
- u64 __val = native_read_msr((msr)); \
+ u64 __val = common_read_msr((msr)); \
(void)((low) = (u32)__val); \
(void)((high) = (u32)(__val >> 32)); \
} while (0)
static inline void wrmsr(u32 msr, u32 low, u32 high)
{
- native_write_msr(msr, (u64)high << 32 | low);
+ common_write_msr(msr, (u64)high << 32 | low);
}
#define rdmsrq(msr, val) \
- ((val) = native_read_msr((msr)))
+ ((val) = common_read_msr((msr)))
static inline void wrmsrq(u32 msr, u64 val)
{
- native_write_msr(msr, val);
+ common_write_msr(msr, val);
}
/* wrmsr with exception handling */
static inline int wrmsrq_safe(u32 msr, u64 val)
{
- return native_write_msr_safe(msr, val);
+ return common_write_msr_safe(msr, val);
}
/* rdmsr with exception handling */
#define rdmsr_safe(msr, low, high) \
({ \
u64 __val; \
- int __err = native_read_msr_safe((msr), &__val); \
+ int __err = common_read_msr_safe((msr), &__val); \
(*low) = (u32)__val; \
(*high) = (u32)(__val >> 32); \
__err; \
@@ -217,7 +228,7 @@ static inline int wrmsrq_safe(u32 msr, u64 val)
static inline int rdmsrq_safe(u32 msr, u64 *p)
{
- return native_read_msr_safe(msr, p);
+ return common_read_msr_safe(msr, p);
}
static __always_inline u64 rdpmc(int counter)
