Re: [PATCH v4 0/2] Move ASID test to vhost-vdpa net initialization

[Lei Yang]

QE did a sanity test on v4 of this series using the vdpa_sim
device,everything is working fine.

Tested-by: Lei Yang <leiyang@redhat.com>

On Fri, May 26, 2023 at 11:31 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> QEMU v8.0 is able to switch dynamically between vhost-vdpa passthrough
> and SVQ mode as long as the net device does not have CVQ.  The net device
> state followed (and migrated) by CVQ requires special care.
>
> A pre-requisite to add CVQ to that framework is to determine if devices with
> CVQ are migratable or not at initialization time.  The solution to it is to
> always shadow only CVQ, and vq groups and ASID are used for that.
>
> However, current qemu version only checks ASID at device start (as "driver set
> DRIVER_OK status bit"), not at device initialization.  A check at
> initialization time is required.  Otherwise, the guest would be able to set
> and remove migration blockers at will [1].
>
> This series is a requisite for migration of vhost-vdpa net devices with CVQ.
> However it already makes sense by its own, as it reduces the number of ioctls
> at migration time, decreasing the error paths there.
>
> [1] 
> https://lore.kernel.org/qemu-devel/2616f0cd-f9e8-d183-ea78-db1be4825d9c@redhat.com/
> ---
> v4:
> * Only probe one of MQ or !MQ.
> * Merge vhost_vdpa_cvq_is_isolated in vhost_vdpa_probe_cvq_isolation
> * Call ioctl directly instead of adding functions.
>
> v3:
> * Only record cvq_isolated, true if the device have cvq isolated in both !MQ
> * and MQ configurations.
> * Drop the cache of cvq group, it can be done on top
>
> v2:
> * Take out the reset of the device from vhost_vdpa_cvq_is_isolated
>   (reported by Lei Yang).
> * Expand patch messages by Stefano G. questions.
>
> Eugenio Pérez (2):
>   vdpa: return errno in vhost_vdpa_get_vring_group error
>   vdpa: move CVQ isolation check to net_init_vhost_vdpa
>
>  net/vhost-vdpa.c | 147 ++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 112 insertions(+), 35 deletions(-)
>
> --
> 2.31.1
>
>