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

[Stefano Garzarella <sgarzare@redhat.com>]

On Sat, Jan 30, 2021 at 07:33:08PM +0800, Yongji Xie wrote:
>On Fri, Jan 29, 2021 at 11:04 PM Stefano Garzarella <sgarzare@redhat.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@bytedance.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.

Okay, I'll do it.

Thanks,
Stefano