On Fri, Nov 20, 2020 at 07:50:44PM +0100, Eugenio Pérez wrote:
> This function is just used for a few commits, so SW LM is developed
> incrementally, and it is deleted after it is useful.
>
> For a few commits, only the events (irqfd, eventfd) are forwarded.
s/eventfd/ioeventfd/ (irqfd is also an eventfd)
> +bool virtio_queue_get_used_notify_split(VirtQueue *vq)
> +{
> + VRingMemoryRegionCaches *caches;
> + hwaddr pa = offsetof(VRingUsed, flags);
> + uint16_t flags;
> +
> + RCU_READ_LOCK_GUARD();
> +
> + caches = vring_get_region_caches(vq);
> + assert(caches);
> + flags = virtio_lduw_phys_cached(vq->vdev, &caches->used, pa);
> + return !(VRING_USED_F_NO_NOTIFY & flags);
> +}
QEMU stores the notification status:
void virtio_queue_set_notification(VirtQueue *vq, int enable)
{
vq->notification = enable; <---- here
if (!vq->vring.desc) {
return;
}
if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
virtio_queue_packed_set_notification(vq, enable);
} else {
virtio_queue_split_set_notification(vq, enable);
I'm wondering why it's necessary to fetch from guest RAM instead of
using vq->notification? It also works for both split and packed
queues so the code would be simpler.
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