linux-kernel - Re: [PATCH RFC v8 02/11] vhost: use batched get_vq

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Message-ID: <CAJaqyWc3C_Td_SpV97CuemkQH9vH+EL3sGgeWGE82E5gYxZNCA@mail.gmail.com>
Date:   Tue, 23 Jun 2020 09:00:57 +0200
From:   Eugenio Perez Martin <eperezma@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        linux-kernel@...r.kernel.org, kvm list <kvm@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH RFC v8 02/11] vhost: use batched get_vq_desc version

On Tue, Jun 23, 2020 at 4:51 AM Jason Wang <jasowang@...hat.com> wrote:
>
>
> On 2020/6/23 上午12:00, Michael S. Tsirkin wrote:
> > On Wed, Jun 17, 2020 at 11:19:26AM +0800, Jason Wang wrote:
> >> On 2020/6/11 下午7:34, Michael S. Tsirkin wrote:
> >>>    static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
> >>>    {
> >>>     kfree(vq->descs);
> >>> @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
> >>>     for (i = 0; i < dev->nvqs; ++i) {
> >>>             vq = dev->vqs[i];
> >>>             vq->max_descs = dev->iov_limit;
> >>> +           if (vhost_vq_num_batch_descs(vq) < 0) {
> >>> +                   return -EINVAL;
> >>> +           }
> >> This check breaks vdpa which set iov_limit to zero. Consider iov_limit is
> >> meaningless to vDPA, I wonder we can skip the test when device doesn't use
> >> worker.
> >>
> >> Thanks
> > It doesn't need iovecs at all, right?
> >
> > -- MST
>
>
> Yes, so we may choose to bypass the iovecs as well.
>
> Thanks
>

I think that the kmalloc_array returns ZERO_SIZE_PTR for all of them
in that case, so I didn't bother to skip the kmalloc_array parts.
Would you prefer to skip them all and let them NULL? Or have I
misunderstood what you mean?

Thanks!