x86/idle: Convert force_mwait_ipi_wakeup to X86_BUG_MONITOR

We're going to want alternative-patch based on it.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
(cherry picked from commit b0ca0f93f4)

xen/arch/x86/acpi/cpu_idle.c

@@ -452,14 +452,8 @@ static int __init cf_check cpu_idle_key_init(void)
 }
 __initcall(cpu_idle_key_init);
 
-/* Force sending of a wakeup IPI regardless of mwait usage. */
-bool __ro_after_init force_mwait_ipi_wakeup;
-
 bool arch_skip_send_event_check(unsigned int cpu)
 {
-    if ( force_mwait_ipi_wakeup )
-        return false;
-
     return false;
 }
 

xen/arch/x86/cpu/intel.c

@@ -436,7 +436,7 @@ static void __init probe_mwait_errata(void)
     {
         printk(XENLOG_WARNING
                "Forcing IPI MWAIT wakeup due to CPU erratum\n");
-        force_mwait_ipi_wakeup = true;
+        setup_force_cpu_cap(X86_BUG_MONITOR);
     }
 }
 

xen/arch/x86/include/asm/cpufeatures.h

@@ -53,6 +53,7 @@ XEN_CPUFEATURE(USE_VMCALL,        X86_SYNTH(30)) /* Use VMCALL instead of VMMCAL
 #define X86_BUG_CLFLUSH_MFENCE    X86_BUG( 2) /* MFENCE needed to serialise CLFLUSH */
 #define X86_BUG_IBPB_NO_RET       X86_BUG( 3) /* IBPB doesn't flush the RSB/RAS */
 #define X86_BUG_CLFLUSH_MONITOR   X86_BUG( 4) /* MONITOR requires CLFLUSH */
+#define X86_BUG_MONITOR           X86_BUG( 5) /* MONITOR doesn't always notice writes (force IPIs) */
 
 #define X86_SPEC_NO_LFENCE_ENTRY_PV X86_BUG(16) /* (No) safety LFENCE for SPEC_CTRL_ENTRY_PV. */
 #define X86_SPEC_NO_LFENCE_ENTRY_INTR X86_BUG(17) /* (No) safety LFENCE for SPEC_CTRL_ENTRY_INTR. */

xen/arch/x86/include/asm/mwait.h

@@ -13,9 +13,6 @@
 
 #define MWAIT_ECX_INTERRUPT_BREAK	0x1
 
-/* Force sending of a wakeup IPI regardless of mwait usage. */
-extern bool force_mwait_ipi_wakeup;
-
 void mwait_idle_with_hints(unsigned int eax, unsigned int ecx);
 bool mwait_pc10_supported(void);