Message-ID: <4BA1AC4A.2070402@lab.ntt.co.jp>
Date: Thu, 18 Mar 2010 13:30:02 +0900
From: OHMURA Kei <ohmura.kei@lab.ntt.co.jp>
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Subject: [Qemu-devel] virtio_blk_load() question
To: "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: ohmura.kei@lab.ntt.co.jp, Avi Kivity <avi@redhat.com>, Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>

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;
...
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?

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;