[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers a
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed |
Date: |
Wed, 12 Dec 2012 14:50:50 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Wed, Dec 12, 2012 at 12:51:01PM +0200, Michael S. Tsirkin wrote:
> Add sanity check to address the following concern:
>
> During migration, all we pass the index of the request;
> the rest can be re-read from the ring.
>
> This is not generally enough if any available requests are outstanding.
> Imagine a ring of size 4. Below A means available U means used.
>
> A 1
> A 2
> U 2
> A 2
> U 2
> A 2
> U 2
> A 2
> U 2
>
> At this point available ring has wrapped around, the only
> way to know head 1 is outstanding is because backend
> has stored this info somewhere.
>
> The reason we manage to migrate without tracking this in migration
> state is because we flush outstanding requests before
> migration.
> This flush is device-specific though, let's add
> a safeguard in virtio core to ensure it's done properly.
>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
>
> Changes from v1:
> v1 was against the wrong tree, it didn't build against qemu.git
>
> hw/virtio.c | 2 ++
> 1 file changed, 2 insertions(+)
VirtIOBlock->rq can trigger the assertion.
IIUC hw/virtio-blk.c may handle I/O errors by keeping the request
pending and on a list (->rq). This allows the user to restart them
after, for example, adding more space to the host file system containing
the disk image file.
We keep a list of failed requests and we migrate this list. So I think
inuse != 0 when migrating with pending failed I/O requests.
Stefan
- [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Michael S. Tsirkin, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed,
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Paolo Bonzini, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Michael S. Tsirkin, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Paolo Bonzini, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Michael S. Tsirkin, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Paolo Bonzini, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Michael S. Tsirkin, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Paolo Bonzini, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Michael S. Tsirkin, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Paolo Bonzini, 2012/12/12
- Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding buffers are flushed, Michael S. Tsirkin, 2012/12/12