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

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Date:   Thu, 28 Jan 2021 11:11:49 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     Xie Yongji <xieyongji@...edance.com>, mst@...hat.com,
        stefanha@...hat.com, parav@...dia.com, bob.liu@...cle.com,
        hch@...radead.org, rdunlap@...radead.org, willy@...radead.org,
        viro@...iv.linux.org.uk, axboe@...nel.dk, bcrl@...ck.org,
        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: [RFC v3 03/11] vdpa: Remove the restriction that only supports
 virtio-net devices


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


>
> Thanks,
> Stefano
>