On Fri, Sep 04, 2015 at 10:54:26AM +0200, Cornelia Huck wrote:
> We allow guests to change the size of the virtqueue rings by supplying
> a number of buffers that is different from the number of buffers the
> device was initialized with. Current code has some problems, however,
> since reset does not reset the ringsizes to the default values (as this
> is not saved anywhere).
>
> Let's extend the core code to keep track of the default ringsizes and
> migrate them once the guest changed them for any of the virtqueues
> for a device.
>
> Signed-off-by: Cornelia Huck <cornelia.h...@de.ibm.com>
> ---
> hw/virtio/virtio.c | 63
> ++++++++++++++++++++++++++++++++++++++++++++++
> include/hw/virtio/virtio.h | 1 +
> 2 files changed, 64 insertions(+)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 788b556..687116e 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -60,6 +60,7 @@ typedef struct VRingUsed
> typedef struct VRing
> {
> unsigned int num;
> + unsigned int num_default;
> unsigned int align;
> hwaddr desc;
> hwaddr avail;
> @@ -633,7 +634,9 @@ void virtio_reset(void *opaque)
> vdev->vq[i].signalled_used = 0;
> vdev->vq[i].signalled_used_valid = false;
> vdev->vq[i].notification = true;
> + vdev->vq[i].vring.num = vdev->vq[i].vring.num_default;
> }
> + vdev->non_default_ringsizes = false;
> }
>
> uint32_t virtio_config_readb(VirtIODevice *vdev, uint32_t addr)
> @@ -855,6 +858,10 @@ void virtio_queue_set_num(VirtIODevice *vdev, int n, int
> num)
> return;
> }
> vdev->vq[n].vring.num = num;
> + if (num != vdev->vq[n].vring.num_default) {
> + /* save ringsizes once one of them has been changed */
> + vdev->non_default_ringsizes = true;
> + }
> }
>
> VirtQueue *virtio_vector_first_queue(VirtIODevice *vdev, uint16_t vector)
> @@ -964,6 +971,7 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int
> queue_size,
> abort();
>
> vdev->vq[i].vring.num = queue_size;
> + vdev->vq[i].vring.num_default = queue_size;
> vdev->vq[i].vring.align = VIRTIO_PCI_VRING_ALIGN;
> vdev->vq[i].handle_output = handle_output;
>
> @@ -977,6 +985,7 @@ void virtio_del_queue(VirtIODevice *vdev, int n)
> }
>
> vdev->vq[n].vring.num = 0;
> + vdev->vq[n].vring.num_default = 0;
> }
>
> void virtio_irq(VirtQueue *vq)
> @@ -1056,6 +1065,13 @@ static bool virtio_virtqueue_needed(void *opaque)
> return virtio_host_has_feature(vdev, VIRTIO_F_VERSION_1);
> }
>
> +static bool virtio_ringsize_needed(void *opaque)
> +{
> + VirtIODevice *vdev = opaque;
> +
> + return vdev->non_default_ringsizes;
> +}
> +
> static void put_virtqueue_state(QEMUFile *f, void *pv, size_t size)
> {
> VirtIODevice *vdev = pv;
> @@ -1104,6 +1120,52 @@ static const VMStateDescription
> vmstate_virtio_virtqueues = {
> }
> };
>
> +static void put_ringsize_state(QEMUFile *f, void *pv, size_t size)
> +{
> + VirtIODevice *vdev = pv;
> + int i;
> +
> + for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
> + qemu_put_be32(f, vdev->vq[i].vring.num_default);
> + }
> +}
> +
> +static int get_ringsize_state(QEMUFile *f, void *pv, size_t size)
> +{
> + VirtIODevice *vdev = pv;
> + int i;
> +
> + for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
> + vdev->vq[i].vring.num_default = qemu_get_be32(f);
> + }
> + return 0;
> +}
> +
> +static VMStateInfo vmstate_info_ringsize = {
> + .name = "ringsize_state",
> + .get = get_ringsize_state,
> + .put = put_ringsize_state,
> +};
> +
> +static const VMStateDescription vmstate_virtio_ringsize = {
> + .name = "virtio/ringsize",
> + .version_id = 1,
> + .minimum_version_id = 1,
> + .needed = &virtio_ringsize_needed,
> + .fields = (VMStateField[]) {
> + {
> + .name = "ringsize",
> + .version_id = 0,
> + .field_exists = NULL,
> + .size = 0,
> + .info = &vmstate_info_ringsize,
> + .flags = VMS_SINGLE,
> + .offset = 0,
> + },
> + VMSTATE_END_OF_LIST()
> + }
> +};
> +
> static const VMStateDescription vmstate_virtio_device_endian = {
> .name = "virtio/device_endian",
> .version_id = 1,
> @@ -1138,6 +1200,7 @@ static const VMStateDescription vmstate_virtio = {
> &vmstate_virtio_device_endian,
> &vmstate_virtio_64bit_features,
> &vmstate_virtio_virtqueues,
> + &vmstate_virtio_ringsize,
> NULL
> }
> };
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index cccae89..29870c8 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -90,6 +90,7 @@ struct VirtIODevice
> VMChangeStateEntry *vmstate;
> char *bus_name;
> uint8_t device_endian;
> + bool non_default_ringsizes;
Let's not try to track this separately. Just go over
rings before migration, and check whether guest changed
anything.
> QLIST_HEAD(, VirtQueue) *vector_queues;
> };
>
> --
> 2.3.8
