linux-kernel - [RFC PATCH v2 09/34] x86/msr: Add the native

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Message-ID: <20250422082216.1954310-10-xin@zytor.com>
Date: Tue, 22 Apr 2025 01:21:50 -0700
From: "Xin Li (Intel)" <xin@...or.com>
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Subject: [RFC PATCH v2 09/34] 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@...or.com>
---

Change in v2:
* Split into two changes and add the native_rdmsrl() helper in the
  first one with a proper explanation (Ingo).
---
 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 b50cbd3299b3..2ab8effea4cd 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -112,6 +112,11 @@ 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)
 
-- 
2.49.0