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Commit caa057a2 authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
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KVM: X86: Provide a capability to disable HLT intercepts 



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: default avatarWanpeng Li <wanpengli@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4d5422ce

Documentation/virtual/kvm/api.txt

+2 −0
Original line number Diff line number Diff line
@@ -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.

----------------------

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

arch/x86/kvm/cpuid.c

+5 −0
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/svm.c

+3 −1
Original line number Diff line number Diff line
@@ -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;

arch/x86/kvm/vmx.c

+24 −0
Original line number Diff line number Diff line
@@ -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;

}