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KVM: X86: Provide a capability to disable HLT intercepts

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If host CPUs are dedicated to a VM, we can avoid VM exits on HLT.
This patch adds the per-VM capability to disable them.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Wanpeng Li 2018-03-12 04:53:03 -07:00 committed by Paolo Bonzini
parent 4d5422cea3
commit caa057a2ca
7 changed files with 46 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
Documentation/virtual/kvm/api.txt
View file

@ -4367,6 +4367,7 @@ Returns: 0 on success, -EINVAL when args[0] contains invalid exits
Valid bits in args[0] are
#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
Enabling this capability on a VM provides userspace with a way to no
longer intercept some instructions for improved latency in some
@ -4375,6 +4376,7 @@ physical CPUs. More bits can be added in the future; userspace can
just pass the KVM_CHECK_EXTENSION result to KVM_ENABLE_CAP to disable
all such vmexits.
Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits.
8. Other capabilities.
----------------------

1
arch/x86/include/asm/kvm_host.h
View file

@ -812,6 +812,7 @@ struct kvm_arch {
gpa_t wall_clock;
bool mwait_in_guest;
bool hlt_in_guest;
bool ept_identity_pagetable_done;
gpa_t ept_identity_map_addr;

5
arch/x86/kvm/cpuid.c
View file

@ -135,6 +135,11 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
return -EINVAL;
}
best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
if (kvm_hlt_in_guest(vcpu->kvm) && best &&
(best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
/* Update physical-address width */
vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
kvm_mmu_reset_context(vcpu);

4
arch/x86/kvm/svm.c
View file

@ -1380,7 +1380,6 @@ static void init_vmcb(struct vcpu_svm *svm)
set_intercept(svm, INTERCEPT_RDPMC);
set_intercept(svm, INTERCEPT_CPUID);
set_intercept(svm, INTERCEPT_INVD);
set_intercept(svm, INTERCEPT_HLT);
set_intercept(svm, INTERCEPT_INVLPG);
set_intercept(svm, INTERCEPT_INVLPGA);
set_intercept(svm, INTERCEPT_IOIO_PROT);
@ -1403,6 +1402,9 @@ static void init_vmcb(struct vcpu_svm *svm)
set_intercept(svm, INTERCEPT_MWAIT);
}
if (!kvm_hlt_in_guest(svm->vcpu.kvm))
set_intercept(svm, INTERCEPT_HLT);
control->iopm_base_pa = __sme_set(iopm_base);
control->msrpm_base_pa = __sme_set(__pa(svm->msrpm));
control->int_ctl = V_INTR_MASKING_MASK;

24
arch/x86/kvm/vmx.c
View file

@ -2556,6 +2556,19 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit
return 0;
}
static void vmx_clear_hlt(struct kvm_vcpu *vcpu)
{
/*
* Ensure that we clear the HLT state in the VMCS. We don't need to
* explicitly skip the instruction because if the HLT state is set,
* then the instruction is already executing and RIP has already been
* advanced.
*/
if (kvm_hlt_in_guest(vcpu->kvm) &&
vmcs_read32(GUEST_ACTIVITY_STATE) == GUEST_ACTIVITY_HLT)
vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
}
static void vmx_queue_exception(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@ -2586,6 +2599,8 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu)
intr_info |= INTR_TYPE_HARD_EXCEPTION;
vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
vmx_clear_hlt(vcpu);
}
static bool vmx_rdtscp_supported(void)
@ -5545,6 +5560,8 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx)
if (kvm_mwait_in_guest(vmx->vcpu.kvm))
exec_control &= ~(CPU_BASED_MWAIT_EXITING |
CPU_BASED_MONITOR_EXITING);
if (kvm_hlt_in_guest(vmx->vcpu.kvm))
exec_control &= ~CPU_BASED_HLT_EXITING;
return exec_control;
}
@ -5906,6 +5923,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
update_exception_bitmap(vcpu);
vpid_sync_context(vmx->vpid);
if (init_event)
vmx_clear_hlt(vcpu);
}
/*
@ -5976,6 +5995,8 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu)
} else
intr |= INTR_TYPE_EXT_INTR;
vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr);
vmx_clear_hlt(vcpu);
}
static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
@ -6006,6 +6027,8 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR);
vmx_clear_hlt(vcpu);
}
static bool vmx_get_nmi_mask(struct kvm_vcpu *vcpu)
@ -12347,6 +12370,7 @@ static int vmx_pre_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
vmx->nested.smm.vmxon = vmx->nested.vmxon;
vmx->nested.vmxon = false;
vmx_clear_hlt(vcpu);
return 0;
}

3
arch/x86/kvm/x86.c
View file

@ -2878,6 +2878,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
r = KVM_CLOCK_TSC_STABLE;
break;
case KVM_CAP_X86_DISABLE_EXITS:
r |= KVM_X86_DISABLE_EXITS_HTL;
if(kvm_can_mwait_in_guest())
r |= KVM_X86_DISABLE_EXITS_MWAIT;
break;
@ -4232,6 +4233,8 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) &&
kvm_can_mwait_in_guest())
kvm->arch.mwait_in_guest = true;
if (cap->args[0] & KVM_X86_DISABLE_EXITS_HTL)
kvm->arch.hlt_in_guest = true;
r = 0;
break;
default:

9
arch/x86/kvm/x86.h
View file

@ -265,11 +265,18 @@ static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec)
})
#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT)
#define KVM_X86_DISABLE_EXITS_HTL (1 << 1)
#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT | \
KVM_X86_DISABLE_EXITS_HTL)
static inline bool kvm_mwait_in_guest(struct kvm *kvm)
{
return kvm->arch.mwait_in_guest;
}
static inline bool kvm_hlt_in_guest(struct kvm *kvm)
{
return kvm->arch.hlt_in_guest;
}
#endif