From 172a14db53beb6554e8a8019d08986d466cb68c8 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Tue, 23 Dec 2025 01:43:54 -0500
Subject: mos/x86_64: msr: Add wrmsr/rdmsr helpers

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 mos/sys/inc/arch/x86_64/msr.h | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/mos/sys/inc/arch/x86_64/msr.h b/mos/sys/inc/arch/x86_64/msr.h
index 4ccf3c8..5c3e1d1 100644
--- a/mos/sys/inc/arch/x86_64/msr.h
+++ b/mos/sys/inc/arch/x86_64/msr.h
@@ -6,6 +6,8 @@
 #ifndef _MACHINE_MSR_H_
 #define _MACHINE_MSR_H_ 1
 
+#include <sdk/defs.h>
+
 #define IA32_APIC_BASE      0x0000001B
 #define IA32_GS_BASE        0xC0000101
 #define IA32_MTRR_CAP       0x000000FE
@@ -15,4 +17,37 @@
 #define IA32_KERNEL_GS_BASE 0xC0000102
 #define IA32_EFER           0xC0000080
 
+#ifndef __ASSEMBLER__
+ALWAYS_INLINE static inline void
+md_wrmsr(ULONG msr, UQUAD v)
+{
+    ULONG lo, hi;
+
+    lo = v & 0xFFFFFFFF;
+    hi = (v >> 32) & 0xFFFFFFFF;
+
+    ASM(
+        "wrmsr"
+        :
+        : "c" (msr), "a" (lo), "d" (hi)
+        : "memory"
+    );
+}
+
+ALWAYS_INLINE static inline UQUAD
+md_rdmsr(ULONG msr)
+{
+    ULONG lo, hi;
+
+    ASM(
+        "rdmsr"
+        : "=a" (lo), "=d" (hi)
+        : "c" (msr)
+        : "memory"
+    );
+
+    return ((UQUAD)hi << 32) | lo;
+}
+
+#endif  /* !__ASSEMBLER__ */
 #endif  /* !_MACHINE_MSR_H_ */
-- 
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