This patch defines a new interface kvm_find_dest_vcpu for
VT-d PI, which can returns the destination vCPU of the
interrupt for guests.
Since VT-d PI cannot handle broadcast/multicast interrupt,
Here we only handle Fixed and Lowest priority interrupts.
The current method of handling guest lowest priority interrtups
is to use a counter 'apic_arb_prio' for each vCPU, we choose the
vCPU with smallest 'apic_arb_prio' and then increase it by 1.
However, for VT-d PI, we cannot re-use this, since we no longer
have control to 'apic_arb_prio' with posted interrupt direct
delivery by Hardware.
Here, we introduce a similar way with 'apic_arb_prio' to handle
guest lowest priority interrtups when VT-d PI is used. Here is the
ideas:
- Each vCPU has a counter 'round_robin_counter'.
- When guests sets an interrupts to lowest priority, we choose
the vCPU with smallest 'round_robin_counter' as the destination,
then increase it.
Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 4 ++++
virt/kvm/irq_comm.c | 41 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 45 insertions(+)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6ed0c30..7a41808 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -358,6 +358,7 @@ struct kvm_vcpu_arch {
struct kvm_lapic *apic; /* kernel irqchip context */
unsigned long apic_attention;
int32_t apic_arb_prio;
+ int32_t round_robin_counter;
int mp_state;
u64 ia32_misc_enable_msr;
bool tpr_access_reporting;
@@ -1093,4 +1094,7 @@ int kvm_pmu_read_pmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
void kvm_handle_pmu_event(struct kvm_vcpu *vcpu);
void kvm_deliver_pmi(struct kvm_vcpu *vcpu);
+bool kvm_find_dest_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
+ struct kvm_vcpu **dest_vcpu);
+
#endif /* _ASM_X86_KVM_HOST_H */
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 963b899..f3c5d69 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -317,6 +317,47 @@ out:
return r;
}
+int kvm_compare_rr_counter(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2)
+{
+ return vcpu1->arch.round_robin_counter -
+ vcpu2->arch.round_robin_counter;
+}
+
+bool kvm_find_dest_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
+ struct kvm_vcpu **dest_vcpu)
+{
+ int i, r = 0;
+ struct kvm_vcpu *vcpu, *dest = NULL;
+
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (!kvm_apic_present(vcpu))
+ continue;
+
+ if (!kvm_apic_match_dest(vcpu, NULL, irq->shorthand,
+ irq->dest_id, irq->dest_mode))
+ continue;
+
+ if (!kvm_is_dm_lowest_prio(irq)) {
+ r++;
+ *dest_vcpu = vcpu;
+ } else if (kvm_lapic_enabled(vcpu)) {
+ if (!dest)
+ dest = vcpu;
+ else if (kvm_compare_rr_counter(vcpu, dest) < 0)
+ dest = vcpu;
+ }
+ }
+
+ if (dest) {
+ dest->arch.round_robin_counter++;
+ *dest_vcpu = dest;
+ return true;
+ } else if (r == 1)
+ return true;
+
+ return false;
+}
+
#define IOAPIC_ROUTING_ENTRY(irq) \
{ .gsi = irq, .type = KVM_IRQ_ROUTING_IRQCHIP, \
.u.irqchip = { .irqchip = KVM_IRQCHIP_IOAPIC, .pin = (irq) } }
--
1.9.1
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