[xen staging-4.19] x86/idle: Convert force_mwait_ipi_wakeup to X86_BUG_MONITOR

[patchbot@xxxxxxx]

commit 41b38d5b4fa5407d9cce1dec3b5261f8907cf61d
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Jul 1 21:40:51 2025 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Mon Jul 7 22:52:15 2025 +0100

    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@xxxxxxxxxx>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    (cherry picked from commit b0ca0f93f47c43f8984981137af07ca3d161e3ec)
---
 xen/arch/x86/acpi/cpu_idle.c           | 6 ------
 xen/arch/x86/cpu/intel.c               | 2 +-
 xen/arch/x86/include/asm/cpufeatures.h | 1 +
 xen/arch/x86/include/asm/mwait.h       | 3 ---
 4 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index a4a6f86943..c42ffb244e 100644
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/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;
 }
 
diff --git a/xen/arch/x86/cpu/intel.c b/xen/arch/x86/cpu/intel.c
index 57258220e8..dbf17be128 100644
--- a/xen/arch/x86/cpu/intel.c
+++ b/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);
     }
 }
 
diff --git a/xen/arch/x86/include/asm/cpufeatures.h 
b/xen/arch/x86/include/asm/cpufeatures.h
index 84c93292c8..56231b00f1 100644
--- a/xen/arch/x86/include/asm/cpufeatures.h
+++ b/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. */
diff --git a/xen/arch/x86/include/asm/mwait.h b/xen/arch/x86/include/asm/mwait.h
index 1f1e39775b..9298f987c4 100644
--- a/xen/arch/x86/include/asm/mwait.h
+++ b/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);
 
--
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