The following commit has been merged into the x86/cpu branch of tip:
Commit-ID: a7dd183f0b3848c056bbeed78ef5d5c52fe94d83
Gitweb: https://git.kernel.org/tip/a7dd183f0b3848c056bbeed78ef5d5c52fe94d83
Author: Patryk Wlazlyn <patryk.wlazlyn@xxxxxxxxxxxxxxx>
AuthorDate: Wed, 05 Feb 2025 17:52:08 +02:00
Committer: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Wed, 05 Feb 2025 10:44:52 -08:00
x86/smp: Allow calling mwait_play_dead with an arbitrary hint
Introduce a helper function to allow offlined CPUs to enter idle states
with a specific MWAIT hint. The new helper will be used in subsequent
patches by the acpi_idle and intel_idle drivers.
No functional change intended.
Signed-off-by: Patryk Wlazlyn <patryk.wlazlyn@xxxxxxxxxxxxxxx>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Link: https://lore.kernel.org/all/20250205155211.329780-2-artem.bityutskiy%40linux.intel.com
---
arch/x86/include/asm/smp.h | 3 +-
arch/x86/kernel/smpboot.c | 88 +++++++++++++++++++------------------
2 files changed, 50 insertions(+), 41 deletions(-)
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index ca073f4..80f8bfd 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -114,6 +114,7 @@ void wbinvd_on_cpu(int cpu);
int wbinvd_on_all_cpus(void);
void smp_kick_mwait_play_dead(void);
+void mwait_play_dead(unsigned int eax_hint);
void native_smp_send_reschedule(int cpu);
void native_send_call_func_ipi(const struct cpumask *mask);
@@ -164,6 +165,8 @@ static inline struct cpumask *cpu_llc_shared_mask(int cpu)
{
return (struct cpumask *)cpumask_of(0);
}
+
+static inline void mwait_play_dead(unsigned int eax_hint) { }
#endif /* CONFIG_SMP */
#ifdef CONFIG_DEBUG_NMI_SELFTEST
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c10850a..8aad14e 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1258,47 +1258,9 @@ void play_dead_common(void)
local_irq_disable();
}
-/*
- * We need to flush the caches before going to sleep, lest we have
- * dirty data in our caches when we come back up.
- */
-static inline void mwait_play_dead(void)
+void __noreturn mwait_play_dead(unsigned int eax_hint)
{
struct mwait_cpu_dead *md = this_cpu_ptr(&mwait_cpu_dead);
- unsigned int eax, ebx, ecx, edx;
- unsigned int highest_cstate = 0;
- unsigned int highest_subcstate = 0;
- int i;
-
- if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
- boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
- return;
- if (!this_cpu_has(X86_FEATURE_MWAIT))
- return;
- if (!this_cpu_has(X86_FEATURE_CLFLUSH))
- return;
-
- eax = CPUID_LEAF_MWAIT;
- ecx = 0;
- native_cpuid(&eax, &ebx, &ecx, &edx);
-
- /*
- * eax will be 0 if EDX enumeration is not valid.
- * Initialized below to cstate, sub_cstate value when EDX is valid.
- */
- if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED)) {
- eax = 0;
- } else {
- edx >>= MWAIT_SUBSTATE_SIZE;
- for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
- if (edx & MWAIT_SUBSTATE_MASK) {
- highest_cstate = i;
- highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
- }
- }
- eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
- (highest_subcstate - 1);
- }
/* Set up state for the kexec() hack below */
md->status = CPUDEAD_MWAIT_WAIT;
@@ -1319,7 +1281,7 @@ static inline void mwait_play_dead(void)
mb();
__monitor(md, 0, 0);
mb();
- __mwait(eax, 0);
+ __mwait(eax_hint, 0);
if (READ_ONCE(md->control) == CPUDEAD_MWAIT_KEXEC_HLT) {
/*
@@ -1342,6 +1304,50 @@ static inline void mwait_play_dead(void)
}
/*
+ * We need to flush the caches before going to sleep, lest we have
+ * dirty data in our caches when we come back up.
+ */
+static inline void mwait_play_dead_cpuid_hint(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+ unsigned int highest_cstate = 0;
+ unsigned int highest_subcstate = 0;
+ int i;
+
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
+ boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
+ return;
+ if (!this_cpu_has(X86_FEATURE_MWAIT))
+ return;
+ if (!this_cpu_has(X86_FEATURE_CLFLUSH))
+ return;
+
+ eax = CPUID_LEAF_MWAIT;
+ ecx = 0;
+ native_cpuid(&eax, &ebx, &ecx, &edx);
+
+ /*
+ * eax will be 0 if EDX enumeration is not valid.
+ * Initialized below to cstate, sub_cstate value when EDX is valid.
+ */
+ if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED)) {
+ eax = 0;
+ } else {
+ edx >>= MWAIT_SUBSTATE_SIZE;
+ for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
+ if (edx & MWAIT_SUBSTATE_MASK) {
+ highest_cstate = i;
+ highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
+ }
+ }
+ eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
+ (highest_subcstate - 1);
+ }
+
+ mwait_play_dead(eax);
+}
+
+/*
* Kick all "offline" CPUs out of mwait on kexec(). See comment in
* mwait_play_dead().
*/
@@ -1391,7 +1397,7 @@ void native_play_dead(void)
play_dead_common();
tboot_shutdown(TB_SHUTDOWN_WFS);
- mwait_play_dead();
+ mwait_play_dead_cpuid_hint();
if (cpuidle_play_dead())
hlt_play_dead();
}
|