On 2021/3/15 17:20, Marc Zyngier wrote:
> On 2021-03-15 09:11, Shenming Lu wrote:
>> On 2021/3/15 16:30, Marc Zyngier wrote:
>>> On 2021-03-13 08:38, Shenming Lu wrote:
>>>> From: Zenghui Yu <yuzenghui@xxxxxxxxxx>
>>>>
>>>> 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@xxxxxxxxxx>
>>>> Signed-off-by: Shenming Lu <lushenming@xxxxxxxxxx>
>>>> ---
>>>> 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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