[PULL 03/21] arm/arm64: KVM: vgic: Factor out level irq processing on guest exit
Christoffer Dall
christoffer.dall at linaro.org
Wed Nov 4 06:49:42 PST 2015
Currently vgic_process_maintenance() processes dealing with a completed
level-triggered interrupt directly, but we are soon going to reuse this
logic for level-triggered mapped interrupts with the HW bit set, so
move this logic into a separate static function.
Probably the most scary part of this commit is convincing yourself that
the current flow is safe compared to the old one. In the following I
try to list the changes and why they are harmless:
Move vgic_irq_clear_queued after kvm_notify_acked_irq:
Harmless because the only potential effect of clearing the queued
flag wrt. kvm_set_irq is that vgic_update_irq_pending does not set
the pending bit on the emulated CPU interface or in the
pending_on_cpu bitmask if the function is called with level=1.
However, the point of kvm_notify_acked_irq is to call kvm_set_irq
with level=0, and we set the queued flag again in
__kvm_vgic_sync_hwstate later on if the level is stil high.
Move vgic_set_lr before kvm_notify_acked_irq:
Also, harmless because the LR are cpu-local operations and
kvm_notify_acked only affects the dist
Move vgic_dist_irq_clear_soft_pend after kvm_notify_acked_irq:
Also harmless, because now we check the level state in the
clear_soft_pend function and lower the pending bits if the level is
low.
Reviewed-by: Eric Auger <eric.auger at linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
---
virt/kvm/arm/vgic.c | 94 +++++++++++++++++++++++++++++++----------------------
1 file changed, 56 insertions(+), 38 deletions(-)
diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 66c6616..367a180 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -107,6 +107,7 @@ static struct vgic_lr vgic_get_lr(const struct kvm_vcpu *vcpu, int lr);
static void vgic_set_lr(struct kvm_vcpu *vcpu, int lr, struct vgic_lr lr_desc);
static struct irq_phys_map *vgic_irq_map_search(struct kvm_vcpu *vcpu,
int virt_irq);
+static int compute_pending_for_cpu(struct kvm_vcpu *vcpu);
static const struct vgic_ops *vgic_ops;
static const struct vgic_params *vgic;
@@ -357,6 +358,11 @@ static void vgic_dist_irq_clear_soft_pend(struct kvm_vcpu *vcpu, int irq)
struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
vgic_bitmap_set_irq_val(&dist->irq_soft_pend, vcpu->vcpu_id, irq, 0);
+ if (!vgic_dist_irq_get_level(vcpu, irq)) {
+ vgic_dist_irq_clear_pending(vcpu, irq);
+ if (!compute_pending_for_cpu(vcpu))
+ clear_bit(vcpu->vcpu_id, dist->irq_pending_on_cpu);
+ }
}
static int vgic_dist_irq_is_pending(struct kvm_vcpu *vcpu, int irq)
@@ -1338,12 +1344,56 @@ epilog:
}
}
+static int process_level_irq(struct kvm_vcpu *vcpu, int lr, struct vgic_lr vlr)
+{
+ int level_pending = 0;
+
+ vlr.state = 0;
+ vlr.hwirq = 0;
+ vgic_set_lr(vcpu, lr, vlr);
+
+ /*
+ * If the IRQ was EOIed (called from vgic_process_maintenance) or it
+ * went from active to non-active (called from vgic_sync_hwirq) it was
+ * also ACKed and we we therefore assume we can clear the soft pending
+ * state (should it had been set) for this interrupt.
+ *
+ * Note: if the IRQ soft pending state was set after the IRQ was
+ * acked, it actually shouldn't be cleared, but we have no way of
+ * knowing that unless we start trapping ACKs when the soft-pending
+ * state is set.
+ */
+ vgic_dist_irq_clear_soft_pend(vcpu, vlr.irq);
+
+ /*
+ * Tell the gic to start sampling the line of this interrupt again.
+ */
+ vgic_irq_clear_queued(vcpu, vlr.irq);
+
+ /* Any additional pending interrupt? */
+ if (vgic_dist_irq_get_level(vcpu, vlr.irq)) {
+ vgic_cpu_irq_set(vcpu, vlr.irq);
+ level_pending = 1;
+ } else {
+ vgic_dist_irq_clear_pending(vcpu, vlr.irq);
+ vgic_cpu_irq_clear(vcpu, vlr.irq);
+ }
+
+ /*
+ * Despite being EOIed, the LR may not have
+ * been marked as empty.
+ */
+ vgic_sync_lr_elrsr(vcpu, lr, vlr);
+
+ return level_pending;
+}
+
static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
{
u32 status = vgic_get_interrupt_status(vcpu);
struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
- bool level_pending = false;
struct kvm *kvm = vcpu->kvm;
+ int level_pending = 0;
kvm_debug("STATUS = %08x\n", status);
@@ -1358,54 +1408,22 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
for_each_set_bit(lr, eisr_ptr, vgic->nr_lr) {
struct vgic_lr vlr = vgic_get_lr(vcpu, lr);
- WARN_ON(vgic_irq_is_edge(vcpu, vlr.irq));
- spin_lock(&dist->lock);
- vgic_irq_clear_queued(vcpu, vlr.irq);
+ WARN_ON(vgic_irq_is_edge(vcpu, vlr.irq));
WARN_ON(vlr.state & LR_STATE_MASK);
- vlr.state = 0;
- vgic_set_lr(vcpu, lr, vlr);
- /*
- * If the IRQ was EOIed it was also ACKed and we we
- * therefore assume we can clear the soft pending
- * state (should it had been set) for this interrupt.
- *
- * Note: if the IRQ soft pending state was set after
- * the IRQ was acked, it actually shouldn't be
- * cleared, but we have no way of knowing that unless
- * we start trapping ACKs when the soft-pending state
- * is set.
- */
- vgic_dist_irq_clear_soft_pend(vcpu, vlr.irq);
/*
* kvm_notify_acked_irq calls kvm_set_irq()
- * to reset the IRQ level. Need to release the
- * lock for kvm_set_irq to grab it.
+ * to reset the IRQ level, which grabs the dist->lock
+ * so we call this before taking the dist->lock.
*/
- spin_unlock(&dist->lock);
-
kvm_notify_acked_irq(kvm, 0,
vlr.irq - VGIC_NR_PRIVATE_IRQS);
- spin_lock(&dist->lock);
-
- /* Any additional pending interrupt? */
- if (vgic_dist_irq_get_level(vcpu, vlr.irq)) {
- vgic_cpu_irq_set(vcpu, vlr.irq);
- level_pending = true;
- } else {
- vgic_dist_irq_clear_pending(vcpu, vlr.irq);
- vgic_cpu_irq_clear(vcpu, vlr.irq);
- }
+ spin_lock(&dist->lock);
+ level_pending |= process_level_irq(vcpu, lr, vlr);
spin_unlock(&dist->lock);
-
- /*
- * Despite being EOIed, the LR may not have
- * been marked as empty.
- */
- vgic_sync_lr_elrsr(vcpu, lr, vlr);
}
}
--
2.1.2.330.g565301e.dirty
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