From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
This patch adds support for KVM_CAP_X86_DISABLE_EXITS. Provides userspace with
per-VM capability(KVM_CAP_X86_DISABLE_EXITS) to not intercept MWAIT/HLT/PAUSE
in order that to improve latency in some workloads.
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: Eduardo Habkost <ehabkost@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
linux-headers/linux/kvm.h | 6 +++++-
target/i386/cpu.h | 2 ++
target/i386/kvm.c | 16 ++++++++++++++++
3 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index a167be8..857df15 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -925,7 +925,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_S390_GS 140
#define KVM_CAP_S390_AIS 141
#define KVM_CAP_SPAPR_TCE_VFIO 142
-#define KVM_CAP_X86_GUEST_MWAIT 143
+#define KVM_CAP_X86_DISABLE_EXITS 143
#define KVM_CAP_ARM_USER_IRQ 144
#define KVM_CAP_S390_CMMA_MIGRATION 145
#define KVM_CAP_PPC_FWNMI 146
@@ -1508,6 +1508,10 @@ struct kvm_assigned_msix_entry {
#define KVM_X2APIC_API_USE_32BIT_IDS (1ULL << 0)
#define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1)
+#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
+#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
+#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
+
/* Available with KVM_CAP_ARM_USER_IRQ */
/* Bits for run->s.regs.device_irq_level */
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 1b219fa..965de1b 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -685,6 +685,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
#define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply Accumulation Single Precision */
#define CPUID_7_0_EDX_SPEC_CTRL (1U << 26) /* Speculation Control */
+#define KVM_PV_UNHALT (1U << 7)
+
#define KVM_HINTS_DEDICATED (1U << 0)
#define CPUID_8000_0008_EBX_IBPB (1U << 12) /* Indirect Branch Prediction Barrier */
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 6c49954..3e99830 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -1029,6 +1029,22 @@ int kvm_arch_init_vcpu(CPUState *cs)
}
}
+ if (env->features[FEAT_KVM_HINTS] & KVM_HINTS_DEDICATED) {
+ int disable_exits = kvm_check_extension(cs->kvm_state, KVM_CAP_X86_DISABLE_EXITS);
+
+ if (disable_exits) {
+ disable_exits &= (KVM_X86_DISABLE_EXITS_MWAIT |
+ KVM_X86_DISABLE_EXITS_HLT |
+ KVM_X86_DISABLE_EXITS_PAUSE);
+ if (env->user_features[FEAT_KVM] & KVM_PV_UNHALT) {
+ disable_exits &= ~KVM_X86_DISABLE_EXITS_HLT;
+ }
+ }
+ if (kvm_vm_enable_cap(cs->kvm_state, KVM_CAP_X86_DISABLE_EXITS, 0, disable_exits)) {
+ error_report("kvm: DISABLE EXITS not supported");
+ }
+ }
+
qemu_add_vm_change_state_handler(cpu_update_state, env);
c = cpuid_find_entry(&cpuid_data.cpuid, 1, 0);
--
2.7.4
