"Michael S. Tsirkin" <mst@xxxxxxxxxx> writes:
> - queue size can actually be 0 which is not a power of 2
Actually, that points to a flaw in the code. When we shut down the
queue, we should ideally reset it to what the device started with,
rather than 0.
See below.
> - fix capability format. PCI spec says:
> The layout of the information is vendor specific, except that the byte
> immediately following the “Next” pointer in the capability structure is
> defined to be a length field.
> This length field provides the number of bytes in the capability
> structure (including the ID and Next pointer bytes).
That part's definitely correct: applied.
Thanks,
Rusty.
Subjet: virtio_pci: save the desired ringsize.
MST points out that 0 isn't a power of 2. This means we can't re-open
a virtio device once we write 0 into the queue length.
We should restore the amount the device originally asked for.
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
diff --git a/drivers/virtio/virtio_pci-common.h b/drivers/virtio/virtio_pci-common.h
index ba1bf81..0e3143b 100644
--- a/drivers/virtio/virtio_pci-common.h
+++ b/drivers/virtio/virtio_pci-common.h
@@ -82,6 +82,9 @@ struct virtio_pci_vq_info {
/* MSI-X vector (or none) */
unsigned msix_vector;
+
+ /* What size did the device *want* this to be? */
+ u16 desired_num;
};
/* the notify function used when creating a virt queue */
diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 0f0e3a6..8b35c2e 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -230,6 +230,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
return ERR_PTR(-ENOMEM);
info->msix_vector = msix_vec;
+ info->desired_num = num;
/* get offset of notification word for this vq (shouldn't wrap) */
off = ioread16(&vp_dev->common->queue_notify_off);
@@ -350,7 +351,7 @@ static void del_vq(struct virtqueue *vq)
vring_del_virtqueue(vq);
/* This is for our own benefit, not the device's! */
- iowrite16(0, &vp_dev->common->queue_size);
+ iowrite16(info->desired_num, &vp_dev->common->queue_size);
iowrite64_twopart(0, &vp_dev->common->queue_desc);
iowrite64_twopart(0, &vp_dev->common->queue_avail);
iowrite64_twopart(0, &vp_dev->common->queue_used);
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