[PATCH v8 5/9] KVM: arm/arm64: Support a vgic interrupt line level sample function

Christoffer Dall
2017-12-13T10:45:58Z

The GIC sometimes need to sample the physical line of a mapped
interrupt. As we know this to be notoriously slow, provide a callback
function for devices (such as the timer) which can do this much faster
than talking to the distributor, for example by comparing a few
in-memory values. Fall back to the good old method of poking the
physical GIC if no callback is provided.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
include/kvm/arm_vgic.h | 13 ++++++++++++-
virt/kvm/arm/arch_timer.c | 3 ++-
virt/kvm/arm/vgic/vgic.c | 13 +++++++++----
3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 8c896540a72c..cdbd142ca7f2 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -130,6 +130,17 @@ struct vgic_irq {
u8 priority;
enum vgic_irq_config config; /* Level or edge */

+ /*
+ * Callback function pointer to in-kernel devices that can tell us the
+ * state of the input level of mapped level-triggered IRQ faster than
+ * peaking into the physical GIC.
+ *
+ * Always called in non-preemptible section and the functions can use
+ * kvm_arm_get_running_vcpu() to get the vcpu pointer for private
+ * IRQs.
+ */
+ bool (*get_input_level)(int vintid);
+
void *owner; /* Opaque pointer to reserve an interrupt
for in-kernel devices. */
};
@@ -331,7 +342,7 @@ void kvm_vgic_init_cpu_hardware(void);
int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
bool level, void *owner);
int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
- u32 vintid);
+ u32 vintid, bool (*get_input_level)(int vindid));
int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int vintid);
bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int vintid);

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index dd5aca05c500..e78ba5e20f74 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -840,7 +840,8 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
return -EINVAL;
}

- ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq);
+ ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
+ NULL);
if (ret)
return ret;

diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 607cbbc27a1c..80c5c609385a 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -144,13 +144,15 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
kfree(irq);
}

-/* Get the input level of a mapped IRQ directly from the physical GIC */
bool vgic_get_phys_line_level(struct vgic_irq *irq)
{
bool line_level;

BUG_ON(!irq->hw);

+ if (irq->get_input_level)
+ return irq->get_input_level(irq->intid);
+
WARN_ON(irq_get_irqchip_state(irq->host_irq,
IRQCHIP_STATE_PENDING,
&line_level));
@@ -436,7 +438,8 @@ int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,

/* @irq->irq_lock must be held */
static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
- unsigned int host_irq)
+ unsigned int host_irq,
+ bool (*get_input_level)(int vindid))
{
struct irq_desc *desc;
struct irq_data *data;
@@ -456,6 +459,7 @@ static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
irq->hw = true;
irq->host_irq = host_irq;
irq->hwintid = data->hwirq;
+ irq->get_input_level = get_input_level;
return 0;
}

@@ -464,10 +468,11 @@ static inline void kvm_vgic_unmap_irq(struct vgic_irq *irq)
{
irq->hw = false;
irq->hwintid = 0;
+ irq->get_input_level = NULL;
}

int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
- u32 vintid)
+ u32 vintid, bool (*get_input_level)(int vindid))
{
struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, vintid);
unsigned long flags;
@@ -476,7 +481,7 @@ int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
BUG_ON(!irq);

spin_lock_irqsave(&irq->irq_lock, flags);
- ret = kvm_vgic_map_irq(vcpu, irq, host_irq);
+ ret = kvm_vgic_map_irq(vcpu, irq, host_irq, get_input_level);
spin_unlock_irqrestore(&irq->irq_lock, flags);
vgic_put_irq(vcpu->kvm, irq);

--
2.14.2