[tip: x86/merge] x86/msr: Add the native_rdmsrq() helper

[tip-bot2 for Xin Li (Intel)]

The following commit has been merged into the x86/merge branch of tip:

Commit-ID:     ed56a309f7e1b05c15702ea1275172d507a606f4
Gitweb:        https://git.kernel.org/tip/ed56a309f7e1b05c15702ea1275172d507a606f4
Author:        Xin Li (Intel) <xin@xxxxxxxxx>
AuthorDate:    Sun, 27 Apr 2025 02:20:20 -07:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Fri, 02 May 2025 10:36:35 +02:00

x86/msr: Add the native_rdmsrq() helper

__rdmsr() is the lowest-level primitive MSR read API, implemented in
assembly code and returning an MSR value in a u64 integer, on top of
which a convenience wrapper native_rdmsr() is defined to return an MSR
value in two u32 integers.  For some reason, native_rdmsrq() is not
defined and __rdmsr() is directly used when it needs to return an MSR
value in a u64 integer.

Add the native_rdmsrq() helper, which is simply an alias of __rdmsr(),
to make native_rdmsr() and native_rdmsrq() a pair of MSR read APIs.

Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Uros Bizjak <ubizjak@xxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20250427092027.1598740-9-xin@xxxxxxxxx
---
 arch/x86/include/asm/msr.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index e5f95a1..adef3ae 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -90,6 +90,11 @@ do {							\
 	(void)((val2) = (u32)(__val >> 32));		\
 } while (0)
 
+static __always_inline u64 native_rdmsrq(u32 msr)
+{
+	return __rdmsr(msr);
+}
+
 #define native_wrmsr(msr, low, high)			\
 	__wrmsr(msr, low, high)