[PATCH v5 17/18] kvm: ioapic: Lazy update IOAPIC EOI

Suravee Suthikulpanit
2019-11-14T20:16:22Z

In-kernel IOAPIC does not receive EOI with AMD SVM AVIC
since the processor accelerate write to APIC EOI register and
does not trap if the interrupt is edge-triggered.

Workaround this by lazy check for pending APIC EOI at the time when
setting new IOPIC irq, and update IOAPIC EOI if no pending APIC EOI.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
arch/x86/kvm/ioapic.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index c57b7bb..6fdd88f 100644
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -48,6 +48,11 @@
static int ioapic_service(struct kvm_ioapic *vioapic, int irq,
bool line_status);

+static void kvm_ioapic_update_eoi_one(struct kvm_vcpu *vcpu,
+ struct kvm_ioapic *ioapic,
+ int trigger_mode,
+ int pin);
+
static unsigned long ioapic_read_indirect(struct kvm_ioapic *ioapic,
unsigned long addr,
unsigned long length)
@@ -174,6 +179,31 @@ static bool rtc_irq_check_coalesced(struct kvm_ioapic *ioapic)
return false;
}

+static void ioapic_lazy_update_eoi(struct kvm_ioapic *ioapic, int irq)
+{
+ int i;
+ struct kvm_vcpu *vcpu;
+ union kvm_ioapic_redirect_entry *entry = &ioapic->redirtbl[irq];
+
+ kvm_for_each_vcpu(i, vcpu, ioapic->kvm) {
+ if (!kvm_apic_match_dest(vcpu, NULL, KVM_APIC_DEST_NOSHORT,
+ entry->fields.dest_id,
+ entry->fields.dest_mode) ||
+ kvm_apic_pending_eoi(vcpu, entry->fields.vector))
+ continue;
+
+ /*
+ * If no longer has pending EOI in LAPICs, update
+ * EOI for this vetor.
+ */
+ rtc_irq_eoi(ioapic, vcpu, entry->fields.vector);
+ kvm_ioapic_update_eoi_one(vcpu, ioapic,
+ entry->fields.trig_mode,
+ irq);
+ break;
+ }
+}
+
static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
int irq_level, bool line_status)
{
@@ -192,6 +222,15 @@ static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
}

/*
+ * AMD SVM AVIC accelerate EOI write and do not trap,
+ * in-kernel IOAPIC will not be able to receive the EOI.
+ * In this case, we do lazy update of the pending EOI when
+ * trying to set IOAPIC irq.
+ */
+ if (kvm_apicv_activated(ioapic->kvm))
+ ioapic_lazy_update_eoi(ioapic, irq);
+
+ /*
* Return 0 for coalesced interrupts; for edge-triggered interrupts,
* this only happens if a previous edge has not been delivered due
* do masking. For level interrupts, the remote_irr field tells
--
1.8.3.1