[PATCH v12 03/37] x86/msr: Add the WRMSRNS instruction support

Xin Li
2023-10-03T06:54:51Z

Add an always inline API __wrmsrns() to embed the WRMSRNS instruction
into the code.

Tested-by: Shan Kang <shan.kang@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
arch/x86/include/asm/msr.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 65ec1965cd28..c284ff9ebe67 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -97,6 +97,19 @@ static __always_inline void __wrmsr(unsigned int msr, u32 low, u32 high)
: : "c" (msr), "a"(low), "d" (high) : "memory");
}

+/*
+ * WRMSRNS behaves exactly like WRMSR with the only difference being
+ * that it is not a serializing instruction by default.
+ */
+static __always_inline void __wrmsrns(u32 msr, u32 low, u32 high)
+{
+ /* Instruction opcode for WRMSRNS; supported in binutils >= 2.40. */
+ asm volatile("1: .byte 0x0f,0x01,0xc6\n"
+ "2:\n"
+ _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_WRMSR)
+ : : "c" (msr), "a"(low), "d" (high));
+}
+
#define native_rdmsr(msr, val1, val2) \
do { \
u64 __val = __rdmsr((msr)); \
@@ -297,6 +310,11 @@ do { \

#endif /* !CONFIG_PARAVIRT_XXL */

+static __always_inline void wrmsrns(u32 msr, u64 val)
+{
+ __wrmsrns(msr, val, val >> 32);
+}
+
/*
* 64-bit version of wrmsr_safe():
*/
--
2.34.1