netdev - Re: [PATCH v10 10/17] virtio: Handle device reset failure in register_virtio

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Date:   Thu, 5 Aug 2021 15:12:39 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Yongji Xie <xieyongji@...edance.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Parav Pandit <parav@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Christian Brauner <christian.brauner@...onical.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, bcrl@...ck.org,
        Jonathan Corbet <corbet@....net>,
        Mika Penttilä <mika.penttila@...tfour.com>,
        Dan Carpenter <dan.carpenter@...cle.com>, joro@...tes.org,
        Greg KH <gregkh@...uxfoundation.org>,
        He Zhe <zhe.he@...driver.com>,
        Liu Xiaodong <xiaodong.liu@...el.com>,
        Joe Perches <joe@...ches.com>, songmuchun@...edance.com,
        virtualization <virtualization@...ts.linux-foundation.org>,
        netdev@...r.kernel.org, kvm <kvm@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 10/17] virtio: Handle device reset failure in
 register_virtio_device()


在 2021/8/4 下午5:07, Yongji Xie 写道:
> On Wed, Aug 4, 2021 at 4:54 PM Jason Wang <jasowang@...hat.com> wrote:
>>
>> 在 2021/8/4 下午4:50, Yongji Xie 写道:
>>> On Wed, Aug 4, 2021 at 4:32 PM Jason Wang <jasowang@...hat.com> wrote:
>>>> 在 2021/8/3 下午5:38, Yongji Xie 写道:
>>>>> On Tue, Aug 3, 2021 at 4:09 PM Jason Wang <jasowang@...hat.com> wrote:
>>>>>> 在 2021/7/29 下午3:34, Xie Yongji 写道:
>>>>>>> The device reset may fail in virtio-vdpa case now, so add checks to
>>>>>>> its return value and fail the register_virtio_device().
>>>>>> So the reset() would be called by the driver during remove as well, or
>>>>>> is it sufficient to deal only with the reset during probe?
>>>>>>
>>>>> Actually there is no way to handle failure during removal. And it
>>>>> should be safe with the protection of software IOTLB even if the
>>>>> reset() fails.
>>>>>
>>>>> Thanks,
>>>>> Yongji
>>>> If this is true, does it mean we don't even need to care about reset
>>>> failure?
>>>>
>>> But we need to handle the failure in the vhost-vdpa case, isn't it?
>>
>> Yes, but:
>>
>> - This patch is for virtio not for vhost, if we don't care virtio, we
>> can avoid the changes
>> - For vhost, there could be two ways probably:
>>
>> 1) let the set_status to report error
>> 2) require userspace to re-read for status
>>
>> It looks to me you want to go with 1) and I'm not sure whether or not
>> it's too late to go with 2).
>>
> Looks like 2) can't work if reset failure happens in
> vhost_vdpa_release() and vhost_vdpa_open().


Yes, you're right.

Thanks


>
> Thanks,
> Yongji
>