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From: Peter Maydell <peter.maydell@linaro.org>
Date: Fri, 29 Jan 2016 14:33:51 +0000
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Subject: Re: [Qemu-devel] [PATCH] Fix virtio migration
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To: "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, Amit Shah <amit.shah@redhat.com>, Cornelia Huck <cornelia.huck@de.ibm.com>, Sascha Silbe <silbe@linux.vnet.ibm.com>

On 29 January 2016 at 13:18, Dr. David Alan Gilbert (git)
<dgilbert@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> I misunderstood the vmstate macro definition when I reworked the
> virtio .get/.put.
> The VMSTATE_STRUCT_VARRAY_KNOWN, was described as being for "a
> variable length array (i.e. _type *_field) but we know the
> length".  However it actually specified operation for arrays embedded in
> the struct (i.e. _type _field[]) since it lacked the VMS_POINTER
> flag. This caused offset calculation to be completely off, examining and
> potentially sending random data instead of the VirtQueue content.
>
> Replace the otherwise unused VMSTATE_STRUCT_VARRAY_KNOWN with a
> VMSTATE_STRUCT_VARRAY_POINTER_KNOWN that includes the VMS_POINTER flag
> (so now actually doing what it advertises) and use it in the virtio
> migration code.

Yeah, these macro names are a bit of a mess. I had an idea ages
back about autogenerating them all as an orthogonal cross product
of the different kinds of thing (and filling in some of the random
gaps in coverage as a side effect), but I never really got anywhere
with it.

thanks
-- PMM