On Wed, May 17, 2023 at 2:26 AM Shannon Nelson <shannon.nelson@xxxxxxx> wrote:
>
> On 5/16/23 12:49 AM, Stefano Garzarella wrote:
> > On Mon, May 15, 2023 at 01:41:12PM -0700, Shannon Nelson wrote:
> >> On 5/9/23 1:46 AM, Stefano Garzarella wrote:
> >>> On Mon, Apr 24, 2023 at 03:50:30PM -0700, Shannon Nelson via
> >>> Virtualization wrote:
> >>>> Use the right structs for PACKED or split vqs when setting and
> >>>> getting the vring base.
> >>>>
> >>>> Signed-off-by: Shannon Nelson <shannon.nelson@xxxxxxx>
> >>>> ---
> >>>> drivers/vhost/vhost.c | 18 +++++++++++++-----
> >>>> drivers/vhost/vhost.h | 8 ++++++--
> >>>> 2 files changed, 19 insertions(+), 7 deletions(-)
> >>>>
> >>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> >>>> index f11bdbe4c2c5..f64efda48f21 100644
> >>>> --- a/drivers/vhost/vhost.c
> >>>> +++ b/drivers/vhost/vhost.c
> >>>> @@ -1633,17 +1633,25 @@ long vhost_vring_ioctl(struct vhost_dev
> >>>> *d, unsigned int ioctl, void __user *arg
> >>>> r = -EFAULT;
> >>>> break;
> >>>> }
> >>>> - if (s.num > 0xffff) {
> >>>> - r = -EINVAL;
> >>>> - break;
> >>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> >>>> + vq->last_avail_idx = s.num & 0xffff;
> >>>> + vq->last_used_idx = (s.num >> 16) & 0xffff;
> >>>> + } else {
> >>>> + if (s.num > 0xffff) {
> >>>> + r = -EINVAL;
> >>>> + break;
> >>>> + }
> >>>> + vq->last_avail_idx = s.num;
> >>>> }
> >>>> - vq->last_avail_idx = s.num;
> >>>> /* Forget the cached index value. */
> >>>> vq->avail_idx = vq->last_avail_idx;
> >>>> break;
> >>>> case VHOST_GET_VRING_BASE:
> >>>> s.index = idx;
> >>>> - s.num = vq->last_avail_idx;
> >>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
> >>>> + s.num = (u32)vq->last_avail_idx |
> >>>> ((u32)vq->last_used_idx << 16);
> >>>> + else
> >>>> + s.num = vq->last_avail_idx;
> >>>
> >>> The changes LGTM, but since we are changing the UAPI, should we
> >>> update the documentation of VHOST_SET_VRING_BASE and
> >>> VHOST_GET_VRING_BASE in include/uapi/linux/vhost.h?
> >>
> >> Correct me if I'm wrong, but I don't think we're changing anything in
> >> the UAPI here, just fixing code to work correctly with what is already
> >> happening.
> >
> > IIUC before this patch VHOST_GET_VRING_BASE and VHOST_SET_VRING_BASE
> > never worked with packed virtqueue, since we were only handling
> > last_avail_idx. Now we are supporting packed virtqueue, handling
> > in vhost_vring_state.num both last_avail_idx and last_used_idx (with
> > wrap counters).
> >
> > For example for VHOST_GET_VRING_BASE where is documented that the first
> > 15 bits are last_avail_idx, the 16th the avail_wrap_counter, and the
> > others are last_used_idx and used_wrap_counter?
> >
> > Maybe I missed something, but since this is UAPI, IMHO we should
> > document the parameters of ioctls at least in
> > include/uapi/linux/vhost.h.
>
> Perhaps Jason already has something written up that could be put in here
> from when he first added the wrap_counter a couple of years ago?
If you meant the virtio driver support for packed, I think it's
different from the context which is vhost here.
I agree with Stefano that we need to update the comments around
GET_VRING_BASE and SET_VRING_BASE, then we are fine.
Thanks
>
> sln
>
> >
> > Thanks,
> > Stefano
> >
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> > To view this discussion on the web visit
> > https://groups.google.com/a/pensando.io/d/msgid/drivers/q6cmfha36sdkgflwwd3pr4sw7rgajag4ahgjbpfjrr76w4o2b6%403yc7zs5u65s4.
>
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