[RFC PATCH 06/45] KVM: arm/arm64: vgic-new: Implement virtual IRQ injection

Andre Przywara
2016-03-25T02:04:36Z

From: Christoffer Dall <christoffer.dall@linaro.org>

Provide a vgic_queue_irq() function which decides whether a given
IRQ needs to be queued to a VCPU's ap_list.
This should be called whenever an IRQ became pending or got enabled,
either as a result of userspace injection, from in-kernel emulated
devices like the architected timer or from MMIO accesses to the
distributor emulation.
Also provides the necessary functions to allow userland to inject an
IRQ to a guest.
[Andre: refactor out vgic_queue_irq()]

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
include/kvm/vgic/vgic.h | 3 +
virt/kvm/arm/vgic/vgic.c | 181 +++++++++++++++++++++++++++++++++++++++++++++++
virt/kvm/arm/vgic/vgic.h | 1 +
3 files changed, 185 insertions(+)

diff --git a/include/kvm/vgic/vgic.h b/include/kvm/vgic/vgic.h
index 659f8b1..f32b284 100644
--- a/include/kvm/vgic/vgic.h
+++ b/include/kvm/vgic/vgic.h
@@ -178,6 +178,9 @@ struct vgic_cpu {
struct list_head ap_list_head;
};

+int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
+ bool level);
+
#define irqchip_in_kernel(k) (!!((k)->arch.vgic.in_kernel))
#define vgic_initialized(k) (false)
#define vgic_ready(k) ((k)->arch.vgic.ready)
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 8e34916..a95aabc 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -19,8 +19,25 @@

#include "vgic.h"

+#define CREATE_TRACE_POINTS
+#include "../trace.h"
+
struct vgic_global kvm_vgic_global_state;

+/*
+ * Locking order is always:
+ * vgic_cpu->ap_list_lock
+ * vgic_irq->irq_lock
+ *
+ * (that is, always take the ap_list_lock before the struct vgic_irq lock).
+ *
+ * When taking more than one ap_list_lock at the same time, always take the
+ * lowest numbered VCPU's ap_list_lock first, so:
+ * vcpuX->vcpu_id < vcpuY->vcpu_id:
+ * spin_lock(vcpuX->arch.vgic_cpu.ap_list_lock);
+ * spin_lock(vcpuY->arch.vgic_cpu.ap_list_lock);
+ */
+
struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
u32 intid)
{
@@ -39,3 +56,167 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
WARN(1, "Looking up struct vgic_irq for reserved INTID");
return NULL;
}
+
+/**
+ * kvm_vgic_target_oracle - compute the target vcpu for an irq
+ *
+ * @irq: The irq to route. Must be already locked.
+ *
+ * Based on the current state of the interrupt (enabled, pending,
+ * active, vcpu and target_vcpu), compute the next vcpu this should be
+ * given to. Return NULL if this shouldn't be injected at all.
+ */
+static struct kvm_vcpu *vgic_target_oracle(struct vgic_irq *irq)
+{
+ /* If the interrupt is active, it must stay on the current vcpu */
+ if (irq->active)
+ return irq->vcpu;
+
+ /* If enabled and pending, it can migrate to a new one */
+ if (irq->enabled && irq->pending)
+ return irq->target_vcpu;
+
+ /* Otherwise, it is considered idle */
+ return NULL;
+}
+
+/*
+ * Only valid injection if changing level for level-triggered IRQs or for a
+ * rising edge.
+ */
+static bool vgic_validate_injection(struct vgic_irq *irq, bool level)
+{
+ switch (irq->config) {
+ case VGIC_CONFIG_LEVEL:
+ return irq->line_level != level;
+ case VGIC_CONFIG_EDGE:
+ return level;
+ default:
+ BUG();
+ }
+}
+
+/*
+ * Check whether an IRQ needs to (and can) be queued to a VCPU's ap list.
+ * Do the queuing if necessary, taking the right locks in the right order.
+ * Returns true when the IRQ was queued, false otherwise.
+ *
+ * Needs to be entered with the IRQ lock already held, but will return
+ * with all locks dropped.
+ */
+bool vgic_queue_irq(struct kvm *kvm, struct vgic_irq *irq)
+{
+ struct kvm_vcpu *vcpu = vgic_target_oracle(irq);
+
+ if (irq->vcpu || !(irq->pending && irq->enabled) || !vcpu) {
+ /*
+ * If this IRQ is already on a VCPU's ap_list, then it
+ * cannot be moved or modified and there is no more work for
+ * us to do.
+ *
+ * Otherwise, if the irq is not pending and enabled, it does
+ * not need to be inserted into an ap_list and there is also
+ * no more work for us to do.
+ */
+ spin_unlock(&irq->irq_lock);
+ return false;
+ }
+
+ /*
+ * We must unlock the irq lock to take the ap_list_lock where
+ * we are going to insert this new pending interrupt.
+ */
+ spin_unlock(&irq->irq_lock);
+
+ /* someone can do stuff here, which we re-check below */
+retry:
+ spin_lock(&vcpu->arch.vgic_cpu.ap_list_lock);
+ spin_lock(&irq->irq_lock);
+
+ /*
+ * Did something change behind our backs?
+ *
+ * There are two cases:
+ * 1) The irq became pending or active behind our backs and/or
+ * the irq->vcpu field was set correspondingly when putting
+ * the irq on an ap_list. Then drop the locks and return.
+ * 2) Someone changed the affinity on this irq behind our
+ * backs and we are now holding the wrong ap_list_lock.
+ * Then drop the locks and try the new VCPU.
+ */
+ if (irq->vcpu || !(irq->pending && irq->enabled)) {
+ spin_unlock(&irq->irq_lock);
+ spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
+ return false;
+ }
+
+ if (irq->target_vcpu != vcpu) {
+ spin_unlock(&irq->irq_lock);
+ spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
+
+ vcpu = irq->target_vcpu;
+ goto retry;
+ }
+
+ list_add_tail(&irq->ap_list, &vcpu->arch.vgic_cpu.ap_list_head);
+ irq->vcpu = vcpu;
+
+ spin_unlock(&irq->irq_lock);
+ spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
+
+ kvm_vcpu_kick(vcpu);
+
+ return true;
+}
+
+static void vgic_update_irq_pending(struct kvm *kvm, struct kvm_vcpu *vcpu,
+ u32 intid, bool level)
+{
+ struct vgic_irq *irq = vgic_get_irq(kvm, vcpu, intid);
+
+ trace_vgic_update_irq_pending(vcpu->vcpu_id, intid, level);
+
+ BUG_ON(in_interrupt());
+
+ spin_lock(&irq->irq_lock);
+
+ if (!vgic_validate_injection(irq, level)) {
+ /* Nothing to see here, move along... */
+ spin_unlock(&irq->irq_lock);
+ return;
+ }
+
+ if (irq->config == VGIC_CONFIG_LEVEL) {
+ irq->line_level = level;
+ irq->pending = level || irq->soft_pending;
+ } else {
+ irq->pending = true;
+ }
+
+ vgic_queue_irq(kvm, irq);
+}
+
+/**
+ * kvm_vgic_inject_irq - Inject an IRQ from a device to the vgic
+ * @kvm: The VM structure pointer
+ * @cpuid: The CPU for PPIs
+ * @intid: The INTID to inject a new state to.
+ * must not be mapped to a HW interrupt.
+ * @level: Edge-triggered: true: to trigger the interrupt
+ * false: to ignore the call
+ * Level-sensitive true: raise the input signal
+ * false: lower the input signal
+ *
+ * The GIC is not concerned with devices being active-LOW or active-HIGH for
+ * level-sensitive interrupts. You can think of the level parameter as 1
+ * being HIGH and 0 being LOW and all devices being active-HIGH.
+ */
+int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
+ bool level)
+{
+ struct kvm_vcpu *vcpu;
+
+ vcpu = kvm_get_vcpu(kvm, cpuid);
+ vgic_update_irq_pending(kvm, vcpu, intid, level);
+ return 0;
+}
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index 61b8d22..e9f4aa6 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -18,5 +18,6 @@

struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
u32 intid);
+bool vgic_queue_irq(struct kvm *kvm, struct vgic_irq *irq);

#endif
--
2.7.3