On 2021/3/15 17:20, Marc Zyngier wrote:

On 2021-03-15 09:11, Shenming Lu wrote:

quoted

On 2021/3/15 16:30, Marc Zyngier wrote:

quoted

On 2021-03-13 08:38, Shenming Lu wrote:

quoted

From: Zenghui Yu <yuzenghui@huawei.com>

When setting the forwarding path of a VLPI (switch to the HW mode),
we can 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 | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
index ac029ba3d337..3b82ab80c2f3 100644
--- a/arch/arm64/kvm/vgic/vgic-v4.c
+++ b/arch/arm64/kvm/vgic/vgic-v4.c

@@ -449,6 +449,24 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,

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

+    /* Transfer pending state */
+    if (irq->pending_latch) {
+        unsigned long flags;
+
+        ret = irq_set_irqchip_state(irq->host_irq,
+                        IRQCHIP_STATE_PENDING,
+                        irq->pending_latch);
+        WARN_RATELIMIT(ret, "IRQ %d", irq->host_irq);
+
+        /*
+         * Clear pending_latch and communicate this state
+         * change via vgic_queue_irq_unlock.
+         */
+        raw_spin_lock_irqsave(&irq->irq_lock, flags);
+        irq->pending_latch = false;
+        vgic_queue_irq_unlock(kvm, irq, flags);
+    }
+
 out:
     mutex_unlock(&its->its_lock);
     return ret;

The read side of the pending state isn't locked, but the write side is.
I'd rather you lock the whole sequence for peace of mind.

Did you mean to lock before emitting the mapping request, Or just before reading
the pending state?

Just before reading the pending state, so that we can't get a concurrent
modification of that state while we make the interrupt pending in the VPT
and clearing it in the emulation.

Get it. I will correct it right now.

Thanks,
Shenming

Thanks,

        M.

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