netdev - RE: [PATCH] vdpa: allow vdpa dev_del management operation to return failure

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Date:   Wed, 8 Jun 2022 10:41:45 +0000
From:   Parav Pandit <parav@...dia.com>
To:     "Dawar, Gautam" <gautam.dawar@....com>,
        Jason Wang <jasowang@...hat.com>
CC:     netdev <netdev@...r.kernel.org>,
        "linux-net-drivers (AMD-Xilinx)" <linux-net-drivers@....com>,
        "Anand, Harpreet" <harpreet.anand@....com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Zhu Lingshan <lingshan.zhu@...el.com>,
        Xie Yongji <xieyongji@...edance.com>,
        Eli Cohen <elic@...dia.com>,
        Si-Wei Liu <si-wei.liu@...cle.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Wan Jiabing <wanjiabing@...o.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] vdpa: allow vdpa dev_del management operation to return
 failure


> From: Dawar, Gautam <gautam.dawar@....com>
> Sent: Wednesday, June 8, 2022 6:30 AM
> To: Jason Wang <jasowang@...hat.com>
> Cc: netdev <netdev@...r.kernel.org>; linux-net-drivers (AMD-Xilinx) <linux-
> net-drivers@....com>; Anand, Harpreet <harpreet.anand@....com>;
> Michael S. Tsirkin <mst@...hat.com>; Zhu Lingshan
> <lingshan.zhu@...el.com>; Xie Yongji <xieyongji@...edance.com>; Eli
> Cohen <elic@...dia.com>; Parav Pandit <parav@...dia.com>; Si-Wei Liu <si-
> wei.liu@...cle.com>; Stefano Garzarella <sgarzare@...hat.com>; Wan
> Jiabing <wanjiabing@...o.com>; Dan Carpenter
> <dan.carpenter@...cle.com>; virtualization <virtualization@...ts.linux-
> foundation.org>; linux-kernel <linux-kernel@...r.kernel.org>
> Subject: RE: [PATCH] vdpa: allow vdpa dev_del management operation to
> return failure
> 
> [AMD Official Use Only - General]
> 
> Hi Gautam:
> [GD>>] Hi Jason,
> 
> On Fri, Jun 3, 2022 at 6:34 PM Gautam Dawar <gautam.dawar@....com>
> wrote:
> >
> > Currently, the vdpa_nl_cmd_dev_del_set_doit() implementation allows
> > returning a value to depict the operation status but the return type
> > of dev_del() callback is void. So, any error while deleting the vdpa
> > device in the vdpa parent driver can't be returned to the management
> > layer.
> 
> I wonder under which cognition we can hit an error in dev_del()?
> [GD>>] In the AMD-Xilinx vDPA driver, on receiving vdpa device deletion
> request, I try to identify if the vdpa device is in use by any virtio-net driver
> (through any vdpa bus driver) by looking at the vdpa device status value. In
> case the vdpa device status is >= VIRTIO_CONFIG_S_DRIVER, -EBUSY is
> returned.
> This is to avoid side-effects as noted in
> https://bugzilla.kernel.org/show_bug.cgi?id=213179 caused by deleting the
> vdpa device when it is being used.
> >
User should be able to delete the device anytime.
Upper layers who are unable to perform teardown sequence should be fixed.