netdev - Re: Re: [RFC v3 03/11] vdpa: Remove the restriction that only supports virtio-net devices

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Date:   Sat, 30 Jan 2021 19:33:08 +0800
From:   Yongji Xie <xieyongji@...edance.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Parav Pandit <parav@...dia.com>, Bob Liu <bob.liu@...cle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Matthew Wilcox <willy@...radead.org>, viro@...iv.linux.org.uk,
        Jens Axboe <axboe@...nel.dk>, bcrl@...ck.org,
        Jonathan Corbet <corbet@....net>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-aio@...ck.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: Re: [RFC v3 03/11] vdpa: Remove the restriction that only
 supports virtio-net devices

On Fri, Jan 29, 2021 at 11:04 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
>
> On Thu, Jan 28, 2021 at 11:11:49AM +0800, Jason Wang wrote:
> >
> >On 2021/1/27 下午4:57, Stefano Garzarella wrote:
> >>On Wed, Jan 27, 2021 at 11:33:03AM +0800, Jason Wang wrote:
> >>>
> >>>On 2021/1/20 下午7:08, Stefano Garzarella wrote:
> >>>>On Wed, Jan 20, 2021 at 11:46:38AM +0800, Jason Wang wrote:
> >>>>>
> >>>>>On 2021/1/19 下午12:59, Xie Yongji wrote:
> >>>>>>With VDUSE, we should be able to support all kinds of virtio devices.
> >>>>>>
> >>>>>>Signed-off-by: Xie Yongji <xieyongji@...edance.com>
> >>>>>>---
> >>>>>> drivers/vhost/vdpa.c | 29 +++--------------------------
> >>>>>> 1 file changed, 3 insertions(+), 26 deletions(-)
> >>>>>>
> >>>>>>diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> >>>>>>index 29ed4173f04e..448be7875b6d 100644
> >>>>>>--- a/drivers/vhost/vdpa.c
> >>>>>>+++ b/drivers/vhost/vdpa.c
> >>>>>>@@ -22,6 +22,7 @@
> >>>>>> #include <linux/nospec.h>
> >>>>>> #include <linux/vhost.h>
> >>>>>> #include <linux/virtio_net.h>
> >>>>>>+#include <linux/virtio_blk.h>
> >>>>>> #include "vhost.h"
> >>>>>>@@ -185,26 +186,6 @@ static long
> >>>>>>vhost_vdpa_set_status(struct vhost_vdpa *v, u8 __user
> >>>>>>*statusp)
> >>>>>>     return 0;
> >>>>>> }
> >>>>>>-static int vhost_vdpa_config_validate(struct vhost_vdpa *v,
> >>>>>>-                      struct vhost_vdpa_config *c)
> >>>>>>-{
> >>>>>>-    long size = 0;
> >>>>>>-
> >>>>>>-    switch (v->virtio_id) {
> >>>>>>-    case VIRTIO_ID_NET:
> >>>>>>-        size = sizeof(struct virtio_net_config);
> >>>>>>-        break;
> >>>>>>-    }
> >>>>>>-
> >>>>>>-    if (c->len == 0)
> >>>>>>-        return -EINVAL;
> >>>>>>-
> >>>>>>-    if (c->len > size - c->off)
> >>>>>>-        return -E2BIG;
> >>>>>>-
> >>>>>>-    return 0;
> >>>>>>-}
> >>>>>
> >>>>>
> >>>>>I think we should use a separate patch for this.
> >>>>
> >>>>For the vdpa-blk simulator I had the same issues and I'm adding
> >>>>a .get_config_size() callback to vdpa devices.
> >>>>
> >>>>Do you think make sense or is better to remove this check in
> >>>>vhost/vdpa, delegating the boundaries checks to
> >>>>get_config/set_config callbacks.
> >>>
> >>>
> >>>A question here. How much value could we gain from
> >>>get_config_size() consider we can let vDPA parent to validate the
> >>>length in its get_config().
> >>>
> >>
> >>I agree, most of the implementations already validate the length,
> >>the only gain is an error returned since get_config() is void, but
> >>eventually we can add a return value to it.
> >
> >
> >Right, one problem here is that. For the virito path, its get_config()
> >returns void. So we can not propagate error to virtio drivers. But it
> >might not be a big issue since we trust kernel virtio driver.
> >
> >So I think it makes sense to change the return value in the vdpa config ops.
>
> Thanks for your feedback!
>
> @Xie do you plan to do this?
>
> Otherwise I can do in my vdpa-blk-sim series, where for now I used this
> patch as is.
>

Hi Stefano, please do in your vdpa-blk-sim series. I have no plan for it now.

Thanks,
Yongji