2017-09-05 22:39-0500, Suravee Suthikulpanit:
SVM AVIC hardware accelerates guest write to APIC_EOI register
(for edge-trigger interrupt), which means it does not trap to KVM.
So, only enable SVM AVIC only in split irqchip mode.
(e.g. launching qemu w/ option '-machine kernel_irqchip=split').
Yeah, hacking TMR to get the VM exit could result in future bugs.
We have to push split irqchip as the deafult in userspaces with this
change.
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
arch/x86/kvm/svm.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d1b3eb4..7ce191b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1292,7 +1291,7 @@ static void init_vmcb(struct vcpu_svm *svm)
set_intercept(svm, INTERCEPT_PAUSE);
}
- if (avic)
+ if (kvm_vcpu_apicv_active(&svm->vcpu))
avic_init_vmcb(svm);
/*
@@ -1594,6 +1593,12 @@ static int avic_init_vcpu(struct vcpu_svm *svm)
if (!avic)
return 0;
+ if (!irqchip_split(svm->vcpu.kvm)) {
The other place used kvm_vcpu_apicv_active() instead of checking
irqchip_split() directly, so I think it would be better to be consistent
and do it here too.
I'd also like if this workaround used !irqchip_split() exactly once.
+ pr_debug("%s: Disable AVIC due to non-split irqchip.\n",
+ __func__);
There is going to be too much of those. pr_debug_once() would be a
better notification. We can also report it in svm_get_enable_apicv().
+ return 0;
+ }
+
ret = avic_init_backing_page(&svm->vcpu);
if (ret)
return ret;
@@ -4388,7 +4393,7 @@ static void svm_set_virtual_x2apic_mode(struct kvm_vcpu *vcpu, bool set)
static bool svm_get_enable_apicv(struct kvm_vcpu *vcpu)
{
- return avic;
+ return avic && irqchip_split(vcpu->kvm);
}
static void svm_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
@@ -4405,7 +4410,7 @@ static void svm_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
struct vcpu_svm *svm = to_svm(vcpu);
struct vmcb *vmcb = svm->vmcb;
- if (!avic)
+ if (!avic || !irqchip_split(svm->vcpu.kvm))
Seems like we want !kvm_vcpu_apicv_active() here too.
return;
vmcb->control.int_ctl &= ~AVIC_ENABLE_MASK;
(separate bug: refresh should be able to enable avic as well.)
thanks.