On 14.09.23 г. 7:47 ч., Xin Li wrote:
Add an always inline API __wrmsrns() to embed the WRMSRNS instruction
into the code.
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
---
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)
Shouldn't this be named wrmsrns_safe since it has exception handling,
similar to the current wrmsrl_safe.
+{
+ /* 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));
+}
+
<snip>
