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

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Date:   Wed, 27 Jan 2021 09:57:28 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Jason Wang <jasowang@...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 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.

Thanks,
Stefano