Subject: x86/idle: Move monitor()/mwait() wrappers into cpu-idle.c
From: Andrew Cooper <[email-masked]>
Date: Tue, 1 Apr 2025 14:59:01 +0100

They're not used by any other translation unit, so shouldn't live in
asm/processor.h, which is included almost everywhere.

Our new toolchain baseline knows the MONITOR/MWAIT instructions, so use them
directly rather than using raw hex.

Change the hint/extention parameters from long to int.  They're specified to
remain 32bit operands even 64-bit mode.

Signed-off-by: Andrew Cooper <[email-masked]>
Reviewed-by: Jan Beulich <[email-masked]>
(cherry picked from commit 61e10fc28ccddff7c72c14acec56dc7ef2b155d1)

diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index 2d8b66c9100a..773eaecc2bbf 100644
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -59,6 +59,19 @@
 
 /*#define DEBUG_PM_CX*/
 
+static always_inline void monitor(
+    const void *addr, unsigned int ecx, unsigned int edx)
+{
+    asm volatile ( "monitor"
+                   :: "a" (addr), "c" (ecx), "d" (edx) );
+}
+
+static always_inline void mwait(unsigned int eax, unsigned int ecx)
+{
+    asm volatile ( "mwait"
+                   :: "a" (eax), "c" (ecx) );
+}
+
 #define GET_HW_RES_IN_NS(msr, val) \
     do { rdmsrl(msr, val); val = tsc_ticks2ns(val); } while( 0 )
 #define GET_MC6_RES(val)  GET_HW_RES_IN_NS(0x664, val)
@@ -482,7 +495,7 @@ void mwait_idle_with_hints(unsigned int eax, unsigned int ecx)
         mb();
     }
 
-    __monitor(monitor_addr, 0, 0);
+    monitor(monitor_addr, 0, 0);
     smp_mb();
 
     /*
@@ -496,7 +509,7 @@ void mwait_idle_with_hints(unsigned int eax, unsigned int ecx)
         cpumask_set_cpu(cpu, &cpuidle_mwait_flags);
 
         spec_ctrl_enter_idle(info);
-        __mwait(eax, ecx);
+        mwait(eax, ecx);
         spec_ctrl_exit_idle(info);
 
         cpumask_clear_cpu(cpu, &cpuidle_mwait_flags);
@@ -927,9 +940,9 @@ void cf_check acpi_dead_idle(void)
              */
             mb();
             clflush(mwait_ptr);
-            __monitor(mwait_ptr, 0, 0);
+            monitor(mwait_ptr, 0, 0);
             mb();
-            __mwait(cx->address, 0);
+            mwait(cx->address, 0);
         }
     }
     else if ( (current_cpu_data.x86_vendor &
diff --git a/xen/arch/x86/include/asm/processor.h b/xen/arch/x86/include/asm/processor.h
index 8ff96388e8b3..07328d44bf4e 100644
--- a/xen/arch/x86/include/asm/processor.h
+++ b/xen/arch/x86/include/asm/processor.h
@@ -405,23 +405,6 @@ static inline bool_t read_pkru_wd(uint32_t pkru, unsigned int pkey)
     return (pkru >> (pkey * PKRU_ATTRS + PKRU_WRITE)) & 1;
 }
 
-static always_inline void __monitor(const void *eax, unsigned long ecx,
-                                    unsigned long edx)
-{
-    /* "monitor %eax,%ecx,%edx;" */
-    asm volatile (
-        ".byte 0x0f,0x01,0xc8;"
-        : : "a" (eax), "c" (ecx), "d"(edx) );
-}
-
-static always_inline void __mwait(unsigned long eax, unsigned long ecx)
-{
-    /* "mwait %eax,%ecx;" */
-    asm volatile (
-        ".byte 0x0f,0x01,0xc9;"
-        : : "a" (eax), "c" (ecx) );
-}
-
 #define IOBMP_BYTES             8192
 #define IOBMP_INVALID_OFFSET    0x8000