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Commit 0a5fff19 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
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KVM: Do not report TPR write to userspace if new value bigger or equal to a previous one. 



Saves many exits to userspace in a case of IRQ chip in userspace.

Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 615d5193

arch/x86/kvm/svm.c

+4 −0
Original line number Diff line number Diff line
@@ -1862,9 +1862,13 @@ static int emulate_on_interception(struct vcpu_svm *svm, 


static int cr8_write_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)

{

	u8 cr8_prev = kvm_get_cr8(&svm->vcpu);

	/* instruction emulation calls kvm_set_cr8() */

	emulate_instruction(&svm->vcpu, NULL, 0, 0, 0);

	if (irqchip_in_kernel(svm->vcpu.kvm))

		return 1;

	if (cr8_prev <= kvm_get_cr8(&svm->vcpu))

		return 1;

	kvm_run->exit_reason = KVM_EXIT_SET_TPR;

	return 0;

}

arch/x86/kvm/vmx.c

+12 −7
Original line number Diff line number Diff line
@@ -2724,13 +2724,18 @@ static int handle_cr(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) 
			kvm_set_cr4(vcpu, kvm_register_read(vcpu, reg));

			skip_emulated_instruction(vcpu);

			return 1;

		case 8:

			kvm_set_cr8(vcpu, kvm_register_read(vcpu, reg));

		case 8: {

				u8 cr8_prev = kvm_get_cr8(vcpu);

				u8 cr8 = kvm_register_read(vcpu, reg);

				kvm_set_cr8(vcpu, cr8);

				skip_emulated_instruction(vcpu);

				if (irqchip_in_kernel(vcpu->kvm))

					return 1;

				if (cr8_prev <= cr8)

					return 1;

				kvm_run->exit_reason = KVM_EXIT_SET_TPR;

				return 0;

			}

		};

		break;

	case 2: /* clts */