[PATCH v2 2/3] vhost: support PACKED when setting-getting vring_base

Shannon Nelson
Mon, 15 May 2023 20:41:12 -0000

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 at amd.com>
>> ---
>> 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.

sln


>
> Thanks,
> Stefano
>