[PATCH 21/22] KVM: vgic-v4: Track the number of VLPIs per vcpu

Marc Zyngier
2019-11-20T16:52:03Z

In order to find out whether a vcpu is likely to be the target of
VLPIs (and to further optimize the way we deal with those), let's
track the number of VLPIs a vcpu can receive.

This gets implemented with an atomic variable that gets incremented
or decremented on map, unmap and move of a VLPI.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Link: https://lore.kernel.org/r/20191107160412.30301-2-maz@kernel.org
---
include/linux/irqchip/arm-gic-v4.h | 2 ++
virt/kvm/arm/vgic/vgic-init.c | 1 +
virt/kvm/arm/vgic/vgic-its.c | 3 +++
virt/kvm/arm/vgic/vgic-v4.c | 2 ++
4 files changed, 8 insertions(+)

diff --git a/include/linux/irqchip/arm-gic-v4.h b/include/linux/irqchip/arm-gic-v4.h
index ab1396afe08a..5dbcfc65f21e 100644
--- a/include/linux/irqchip/arm-gic-v4.h
+++ b/include/linux/irqchip/arm-gic-v4.h
@@ -32,6 +32,8 @@ struct its_vm {
struct its_vpe {
struct page *vpt_page;
struct its_vm *its_vm;
+ /* per-vPE VLPI tracking */
+ atomic_t vlpi_count;
/* Doorbell interrupt */
int irq;
irq_hw_number_t vpe_db_lpi;
diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 6f50c429196d..b3c5de48064c 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -203,6 +203,7 @@ int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)

INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
raw_spin_lock_init(&vgic_cpu->ap_list_lock);
+ atomic_set(&vgic_cpu->vgic_v3.its_vpe.vlpi_count, 0);

/*
* Enable and configure all SGIs to be edge-triggered and
diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 2be6b66b3856..98c7360d9fb7 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -360,7 +360,10 @@ static int update_affinity(struct vgic_irq *irq, struct kvm_vcpu *vcpu)
if (ret)
return ret;

+ if (map.vpe)
+ atomic_dec(&map.vpe->vlpi_count);
map.vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
+ atomic_inc(&map.vpe->vlpi_count);

ret = its_map_vlpi(irq->host_irq, &map);
}
diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
index 0965fb0c427a..46f875589c47 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -309,6 +309,7 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,

irq->hw = true;
irq->host_irq = virq;
+ atomic_inc(&map.vpe->vlpi_count);

out:
mutex_unlock(&its->its_lock);
@@ -342,6 +343,7 @@ int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,

WARN_ON(!(irq->hw && irq->host_irq == virq));
if (irq->hw) {
+ atomic_dec(&irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count);
irq->hw = false;
ret = its_unmap_vlpi(virq);