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Subject[PATCH 27/31] KVM: SVM: disable CR8 intercept when tpr is not masking interrupts
Date
From: Joerg Roedel <joerg.roedel@amd.com>

This patch disables the intercept of CR8 writes if the TPR is not masking
interrupts. This reduces the total number CR8 intercepts to below 1 percent of
what we have without this patch using Windows 64 bit guests.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---
arch/x86/kvm/svm.c | 31 +++++++++++++++++++++++++++----
1 files changed, 27 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ee2ee83..61bb2cb 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1502,6 +1502,27 @@ static void svm_set_irq(struct kvm_vcpu *vcpu, int irq)
svm_inject_irq(svm, irq);
}

+static void update_cr8_intercept(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_svm *svm = to_svm(vcpu);
+ struct vmcb *vmcb = svm->vmcb;
+ int max_irr, tpr;
+
+ if (!irqchip_in_kernel(vcpu->kvm) || vcpu->arch.apic->vapic_addr)
+ return;
+
+ vmcb->control.intercept_cr_write &= ~INTERCEPT_CR8_MASK;
+
+ max_irr = kvm_lapic_find_highest_irr(vcpu);
+ if (max_irr == -1)
+ return;
+
+ tpr = kvm_lapic_get_cr8(vcpu) << 4;
+
+ if (tpr >= (max_irr & 0xf0))
+ vmcb->control.intercept_cr_write |= INTERCEPT_CR8_MASK;
+}
+
static void svm_intr_assist(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
@@ -1514,14 +1535,14 @@ static void svm_intr_assist(struct kvm_vcpu *vcpu)
SVM_EVTINJ_VEC_MASK;
vmcb->control.exit_int_info = 0;
svm_inject_irq(svm, intr_vector);
- return;
+ goto out;
}

if (vmcb->control.int_ctl & V_IRQ_MASK)
- return;
+ goto out;

if (!kvm_cpu_has_interrupt(vcpu))
- return;
+ goto out;

if (!(vmcb->save.rflags & X86_EFLAGS_IF) ||
(vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK) ||
@@ -1529,12 +1550,14 @@ static void svm_intr_assist(struct kvm_vcpu *vcpu)
/* unable to deliver irq, set pending irq */
vmcb->control.intercept |= (1ULL << INTERCEPT_VINTR);
svm_inject_irq(svm, 0x0);
- return;
+ goto out;
}
/* Okay, we can deliver the interrupt: grab it and update PIC state. */
intr_vector = kvm_cpu_get_interrupt(vcpu);
svm_inject_irq(svm, intr_vector);
kvm_timer_intr_post(vcpu, intr_vector);
+out:
+ update_cr8_intercept(vcpu);
}

static void kvm_reput_irq(struct vcpu_svm *svm)
--
1.5.5


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