Re: [RFC v2 08/13] vdpa: Negotiate _F_SUSPEND feature

[Jason Wang <jasowang@redhat.com>]

在 2023/1/13 16:45, Eugenio Perez Martin 写道:
> On Fri, Jan 13, 2023 at 5:39 AM Jason Wang <jasowang@redhat.com> wrote:
>> On Fri, Jan 13, 2023 at 1:25 AM Eugenio Pérez <eperezma@redhat.com> wrote:
>>> This is needed for qemu to know it can suspend the device to retrieve
>>> its status and enable SVQ with it, so all the process is transparent to
>>> the guest.
>>>
>>> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
>> Acked-by: Jason Wang <jasowang@redhat.com>
>>
>> We probably need to add the resume in the future to have a quick
>> recovery from migration failures.
>>
> The capability of a resume can be useful here but only in a small
> window. During the most time of the migration SVQ is enabled, so in
> the event of a migration failure we may need to reset the whole device
> to enable passthrough again.


Yes.


>
> But maybe is it worth giving a quick review and adding some TODOs
> where it can be useful in this series?


We can start by having a TODO in this series, and leave resume in for 
the future.

Thanks


>
> Thanks!
>
>> Thanks
>>
>>> ---
>>>   hw/virtio/vhost-vdpa.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
>>> index 4296427a69..a61a6b2a74 100644
>>> --- a/hw/virtio/vhost-vdpa.c
>>> +++ b/hw/virtio/vhost-vdpa.c
>>> @@ -659,7 +659,8 @@ static int vhost_vdpa_set_backend_cap(struct vhost_dev *dev)
>>>       uint64_t features;
>>>       uint64_t f = 0x1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2 |
>>>           0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH |
>>> -        0x1ULL << VHOST_BACKEND_F_IOTLB_ASID;
>>> +        0x1ULL << VHOST_BACKEND_F_IOTLB_ASID |
>>> +        0x1ULL << VHOST_BACKEND_F_SUSPEND;
>>>       int r;
>>>
>>>       if (vhost_vdpa_call(dev, VHOST_GET_BACKEND_FEATURES, &features)) {
>>> --
>>> 2.31.1
>>>