On Wed, Dec 12, 2012 at 10:00:37PM +0100, Paolo Bonzini wrote:
> Il 12/12/2012 20:23, Michael S. Tsirkin ha scritto:
> >>> Saving inuse counter is useless. We need to know which requests
> >>> are outstanding if we want to retry them on remote.
> >>
> >> And that's what virtio-blk and virtio-scsi have been doing for years.
> >
> > I don't see it - all I see in save is virtio_save.
>
> static void virtio_blk_save(QEMUFile *f, void *opaque)
> {
> VirtIOBlock *s = opaque;
> VirtIOBlockReq *req = s->rq;
>
> virtio_save(&s->vdev, f);
>
> while (req) {
> qemu_put_sbyte(f, 1);
> qemu_put_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
Ow. Does it really save VirtQueueElement?
typedef struct VirtQueueElement
{
unsigned int index;
unsigned int out_num;
unsigned int in_num;
hwaddr in_addr[VIRTQUEUE_MAX_SIZE];
hwaddr out_addr[VIRTQUEUE_MAX_SIZE];
struct iovec in_sg[VIRTQUEUE_MAX_SIZE];
struct iovec out_sg[VIRTQUEUE_MAX_SIZE];
} VirtQueueElement;
Complete with pointers into qemu memory and all?
That's got to hurt.
All we really need is the index.
> req = req->next;
> }
> qemu_put_sbyte(f, 0);
> }
>
>
> virtio-scsi does it in virtio_scsi_save_request.
>
> > You need to retry A1 on remote. How do you do that? There's
> > no way to find out it has not been completed
> > from the ring itself.
>
> virtio_blk_dma_restart_bh and scsi_dma_restart_bh do it.
>
> Paolo
Okay, so the only bug is inuse getting negative right?
So all we need to do is fix up the inuse value
after restoring the outstanding requests - basically
count the restored buffers and set inuse accordingly.
--
MST
