Re: [PATCH RFC 09/15] hw/virtio/vhost-shadow-virtqueue: specified vring placement

On Mon, Aug 3, 2026 at 5:48 AM Hanna Czenczek <[email protected]> wrote:
>
> On 24.07.26 00:30, Connor Kite wrote:
> > By default svq vrings are placed in an anonymous memory map. As svqs
> > will be leveraged to enable memory isolation in vhost-user, it is useful
> > to be able to place the vrings in a shared isolation memory region.
> >
> > Adds the option to specify vring placement by providing a vring base
> > address before starting the svq.
> >
> > Signed-off-by: Connor Kite <[email protected]>
> > ---
> >   hw/virtio/vhost-shadow-virtqueue.c | 22 +++++++++++++++-------
> >   hw/virtio/vhost-shadow-virtqueue.h |  3 +++
> >   2 files changed, 18 insertions(+), 7 deletions(-)
>
> I would go beyond Stefan and say that I do really ask for explicit
> bounds checking on the area.
>
> Besides that, `vhost_svq_stop()` still always calls `munmap()` on `desc`
> and `used` and that must absolutely not be done in case a fixed location
> was provided.
>
> Also, it would be nicer to have a function to set the base address
> instead of having to modify the svq object directly.
>
> Hanna

Got it!  I now check that the last address in the vring area is not
less than the
first address.  vhost_svq_start now returns an int so that success/error can be
communicated to the caller.

I just moved some existing changes to vhost_svq_stop forward to this patch to
just memset the vring area to 0 if static location is used and vring
pointers are not
null.

vhost_svq_set_base_addr has been added in to remove direct adjustment to the svq
base address.

Best,
Connor