[PATCH] x86/msr: Standardize on 'u32' MSR indices in <asm/msr.h>

[Ingo Molnar <mingo@kernel.org>]

* Xin Li <xin@zytor.com> wrote:

> On 4/1/2025 12:52 AM, Ingo Molnar wrote:
> > > Should we rename the *msrl() functions to *msrq() as part of this
> > > overhaul?
> > Yeah, that's a good idea, and because talk is cheap I just implemented
> > this in the tip:WIP.x86/msr branch with a couple of other cleanups in
> > this area (see the shortlog & diffstat below), but the churn is high:
> > 
> >    144 files changed, 1034 insertions(+), 1034 deletions(-)
> 
> Hi Ingo,
> 
> I noticed that you keep the type of MSR index in these patches as
> "unsigned int".
> 
> I'm thinking would it be better to standardize it as "u32"?
> 
> Because:
> 1) MSR index is placed in ECX to execute MSR instructions, and the
>    high-order 32 bits of RCX are ignored on 64-bit.
> 2) MSR index is encoded as a 32-bit immediate in the new immediate form
>    MSR instructions.

Makes sense - something like the attached patch?

Thanks,

	Ingo

=====================>
From: Ingo Molnar <mingo@kernel.org>
Date: Wed, 9 Apr 2025 21:12:39 +0200
Subject: [PATCH] x86/msr: Standardize on 'u32' MSR indices in <asm/msr.h>

This is the customary type used for hardware ABIs.

Suggested-by: Xin Li <xin@zytor.com>
Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/msr.h | 29 ++++++++++++++---------------
 arch/x86/lib/msr.c         |  4 ++--
 2 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 4ee9ae734c08..20deb58308e5 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -63,12 +63,12 @@ struct saved_msrs {
 DECLARE_TRACEPOINT(read_msr);
 DECLARE_TRACEPOINT(write_msr);
 DECLARE_TRACEPOINT(rdpmc);
-extern void do_trace_write_msr(unsigned int msr, u64 val, int failed);
-extern void do_trace_read_msr(unsigned int msr, u64 val, int failed);
+extern void do_trace_write_msr(u32 msr, u64 val, int failed);
+extern void do_trace_read_msr(u32 msr, u64 val, int failed);
 extern void do_trace_rdpmc(u32 msr, u64 val, int failed);
 #else
-static inline void do_trace_write_msr(unsigned int msr, u64 val, int failed) {}
-static inline void do_trace_read_msr(unsigned int msr, u64 val, int failed) {}
+static inline void do_trace_write_msr(u32 msr, u64 val, int failed) {}
+static inline void do_trace_read_msr(u32 msr, u64 val, int failed) {}
 static inline void do_trace_rdpmc(u32 msr, u64 val, int failed) {}
 #endif
 
@@ -79,7 +79,7 @@ static inline void do_trace_rdpmc(u32 msr, u64 val, int failed) {}
  * think of extending them - you will be slapped with a stinking trout or a frozen
  * shark will reach you, wherever you are! You've been warned.
  */
-static __always_inline u64 __rdmsr(unsigned int msr)
+static __always_inline u64 __rdmsr(u32 msr)
 {
 	DECLARE_ARGS(val, low, high);
 
@@ -91,7 +91,7 @@ static __always_inline u64 __rdmsr(unsigned int msr)
 	return EAX_EDX_VAL(val, low, high);
 }
 
-static __always_inline void __wrmsr(unsigned int msr, u32 low, u32 high)
+static __always_inline void __wrmsr(u32 msr, u32 low, u32 high)
 {
 	asm volatile("1: wrmsr\n"
 		     "2:\n"
@@ -113,7 +113,7 @@ do {							\
 	__wrmsr((msr), (u32)((u64)(val)),		\
 		       (u32)((u64)(val) >> 32))
 
-static inline u64 native_read_msr(unsigned int msr)
+static inline u64 native_read_msr(u32 msr)
 {
 	u64 val;
 
@@ -125,8 +125,7 @@ static inline u64 native_read_msr(unsigned int msr)
 	return val;
 }
 
-static inline u64 native_read_msr_safe(unsigned int msr,
-						      int *err)
+static inline u64 native_read_msr_safe(u32 msr, int *err)
 {
 	DECLARE_ARGS(val, low, high);
 
@@ -142,7 +141,7 @@ static inline u64 native_read_msr_safe(unsigned int msr,
 
 /* Can be uninlined because referenced by paravirt */
 static inline void notrace
-native_write_msr(unsigned int msr, u32 low, u32 high)
+native_write_msr(u32 msr, u32 low, u32 high)
 {
 	__wrmsr(msr, low, high);
 
@@ -152,7 +151,7 @@ native_write_msr(unsigned int msr, u32 low, u32 high)
 
 /* Can be uninlined because referenced by paravirt */
 static inline int notrace
-native_write_msr_safe(unsigned int msr, u32 low, u32 high)
+native_write_msr_safe(u32 msr, u32 low, u32 high)
 {
 	int err;
 
@@ -251,7 +250,7 @@ do {								\
 	(void)((high) = (u32)(__val >> 32));			\
 } while (0)
 
-static inline void wrmsr(unsigned int msr, u32 low, u32 high)
+static inline void wrmsr(u32 msr, u32 low, u32 high)
 {
 	native_write_msr(msr, low, high);
 }
@@ -259,13 +258,13 @@ static inline void wrmsr(unsigned int msr, u32 low, u32 high)
 #define rdmsrq(msr, val)			\
 	((val) = native_read_msr((msr)))
 
-static inline void wrmsrq(unsigned int msr, u64 val)
+static inline void wrmsrq(u32 msr, u64 val)
 {
 	native_write_msr(msr, (u32)(val & 0xffffffffULL), (u32)(val >> 32));
 }
 
 /* wrmsr with exception handling */
-static inline int wrmsr_safe(unsigned int msr, u32 low, u32 high)
+static inline int wrmsr_safe(u32 msr, u32 low, u32 high)
 {
 	return native_write_msr_safe(msr, low, high);
 }
@@ -280,7 +279,7 @@ static inline int wrmsr_safe(unsigned int msr, u32 low, u32 high)
 	__err;							\
 })
 
-static inline int rdmsrq_safe(unsigned int msr, u64 *p)
+static inline int rdmsrq_safe(u32 msr, u64 *p)
 {
 	int err;
 
diff --git a/arch/x86/lib/msr.c b/arch/x86/lib/msr.c
index e18925899f13..4ef7c6dcbea6 100644
--- a/arch/x86/lib/msr.c
+++ b/arch/x86/lib/msr.c
@@ -122,14 +122,14 @@ int msr_clear_bit(u32 msr, u8 bit)
 EXPORT_SYMBOL_GPL(msr_clear_bit);
 
 #ifdef CONFIG_TRACEPOINTS
-void do_trace_write_msr(unsigned int msr, u64 val, int failed)
+void do_trace_write_msr(u32 msr, u64 val, int failed)
 {
 	trace_write_msr(msr, val, failed);
 }
 EXPORT_SYMBOL(do_trace_write_msr);
 EXPORT_TRACEPOINT_SYMBOL(write_msr);
 
-void do_trace_read_msr(unsigned int msr, u64 val, int failed)
+void do_trace_read_msr(u32 msr, u64 val, int failed)
 {
 	trace_read_msr(msr, val, failed);
 }