On 2021/1/5 17:25, Marc Zyngier wrote:

On 2021-01-04 08:16, Shenming Lu wrote:

quoted

From: Zenghui Yu <yuzenghui@huawei.com>

When setting the forwarding path of a VLPI (switch to the HW mode),
we could also transfer the pending state from irq->pending_latch to
VPT (especially in migration, the pending states of VLPIs are restored
into kvm’s vgic first). And we currently send "INT+VSYNC" to trigger
a VLPI to pending.

Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Shenming Lu <redacted>
---
 arch/arm64/kvm/vgic/vgic-v4.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
index f211a7c32704..7945d6d09cdd 100644
--- a/arch/arm64/kvm/vgic/vgic-v4.c
+++ b/arch/arm64/kvm/vgic/vgic-v4.c

@@ -454,6 +454,18 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,

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

+    /* Transfer pending state */
+    ret = irq_set_irqchip_state(irq->host_irq,
+                    IRQCHIP_STATE_PENDING,
+                    irq->pending_latch);
+    WARN_RATELIMIT(ret, "IRQ %d", irq->host_irq);

Why do this if pending_latch is 0, which is likely to be
the overwhelming case?

Yes, there is no need to do this if pending_latch is 0.

quoted

+
+    /*
+     * Let it be pruned from ap_list later and don't bother
+     * the List Register.
+     */
+    irq->pending_latch = false;

What guarantees the pruning? Pruning only happens on vcpu exit,
which means we may have the same interrupt via both the LR and
the stream interface, which I don't believe is legal (it is
like having two LRs holding the same interrupt).

Since the irq's pending_latch is set to false here, it will not be
populated to the LR in vgic_flush_lr_state() (vgic_target_oracle()
will return NULL).

quoted

+
 out:
     mutex_unlock(&its->its_lock);
     return ret;

Thanks,

        M.

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