On (Tue) 26 Jun 2012 [08:01:20], Anthony Liguori wrote:
> On 06/26/2012 05:48 AM, Amit Shah wrote:
> >On (Mon) 25 Jun 2012 [17:59:28], Anthony Liguori wrote:
> >>On 06/25/2012 05:46 PM, Anthony Liguori wrote:
> >>>From: Amit Shah<amit.s...@redhat.com>
> >
> >>>diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> >
> >>>+static void virtio_rng_class_init(ObjectClass *klass, void *data)
> >>>+{
> >>>+ DeviceClass *dc = DEVICE_CLASS(klass);
> >>>+ PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
> >>>+
> >>>+ k->init = virtio_rng_init_pci;
> >>>+ k->exit = virtio_rng_exit_pci;
> >>>+ k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
> >>>+ k->device_id = PCI_DEVICE_ID_VIRTIO_RNG;
> >>>+ k->revision = VIRTIO_PCI_ABI_VERSION;
> >>>+ k->class_id = PCI_CLASS_OTHERS;
> >>
> >>WHQL tends to get very particular about PCI classes. Do we
> >>understand the implications of making this CLASS_OTHERS and WHQL?
> >
> >I've not asked around; will update with info when I get it.
>
> Thanks.
... and I heard back: PCI_CLASS_OTHERS is fine; no problem.
> >>>+/* Send data from a char device over to the guest */
> >>>+static void chr_read(void *opaque, const void *buf, size_t size)
> >>>+{
> >>>+ VirtIORNG *vrng = opaque;
> >>>+ size_t len;
> >>>+ int offset;
> >>>+
> >>>+ if (!is_guest_ready(vrng)) {
> >>>+ return;
> >>>+ }
> >>>+
> >>>+ offset = 0;
> >>>+ while (offset< size) {
> >>>+ if (!pop_an_elem(vrng)) {
> >>>+ break;
> >>>+ }
> >>>+ len = iov_from_buf(vrng->elem.in_sg, vrng->elem.in_num,
> >>>+ buf + offset, 0, size - offset);
> >>>+ offset += len;
> >>>+
> >>>+ virtqueue_push(vrng->vq,&vrng->elem, len);
> >>>+ vrng->popped = false;
> >>>+ }
> >>>+ virtio_notify(&vrng->vdev, vrng->vq);
> >>>+
> >>>+ /*
> >>>+ * Lastly, if we had multiple elems queued by the guest, and we
> >>>+ * didn't have enough data to fill them all, indicate we want more
> >>>+ * data.
> >>>+ */
> >>>+ len = pop_an_elem(vrng);
> >>>+ if (len) {
> >>>+ rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
> >>>+ }
> >>
> >>Because of this above while() loop, you won't see entropy requests
> >>for every request that comes from the guest depending on how data
> >>gets buffered in the socket.
> >
> >So the issue is we currently can't get the iov_size without popping
> >the elem from the vq.
>
> I think we could split out some of the logic in virtqueue_pop to
> implement a virtqueue_peek().
Just sent out a series that adds virtqueue_get_avail_bytes() which
does this. A rebased series on top of that eliminates the need for
popping and save/load of the elem.
Amit
