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[Qemu-devel] Re: virtio_blk_load() question
From: |
Juan Quintela |
Subject: |
[Qemu-devel] Re: virtio_blk_load() question |
Date: |
Thu, 18 Mar 2010 08:37:23 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
OHMURA Kei <address@hidden> wrote:
> Hi,
>
> I have a question regarding virtio_blk_load().
> (qemu-kvm.git d1fa468c1cc03ea362d8fe3ed9269bab4d197510)
>
> VirtIOBlockReq structure is linked list of requests, but it doesn't seem to be
> properly linked in virtio_blk_load().
> ...
> req->next = s->rq;
> s->rq = req->next;
> ...
You are right.
> In this case, we're losing req, and s->rq always point to be same entry.
> If I'm understanding correctly, s->rq is NULL initially,
> and this would be kept.
>
> Although I'm not sure how these requests should be ordered, if the requests
> should be added to the head of list to restore the saved status by
> virtio_blk_save(), I think the following code is correct. However, it seems
> to
> reverse the order of the requests, and I'm wondering whether that is
> appropriate.
>
> Would somebody tell me how virtio_blk_load() is working?
When I ported virtio to vmstate, I was unable to get that list not empty
for more than I tried. It should be not empty in the case of one error
or similar, but I was not able to reproduce it.
> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index b80402d..267b16f 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -457,7 +457,7 @@ static int virtio_blk_load(QEMUFile *f, void *opaque, int
> version_id)
> VirtIOBlockReq *req = virtio_blk_alloc_request(s);
> qemu_get_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
> req->next = s->rq;
> - s->rq = req->next;
> + s->rq = req;
> }
>
> return 0;
I agree this change is ok/needed. Notice that my series ( [PATCH 0/9]
Virtio cleanups) that changes it to a QLIST and fixes it.
(althought again, I was never able to get that list with elements at the
time of migration).
Thanks, Juan.