Re: [PATCH] Revert "virtio_pci: Support surprise removal of virtio pci device"

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Aug 22, 2025 at 12:24:06PM +0000, Parav Pandit wrote:
> 
> > From: Li,Rongqing <lirongqing@baidu.com>
> > Sent: 22 August 2025 03:57 PM
> > 
> > > This reverts commit 43bb40c5b926 ("virtio_pci: Support surprise
> > > removal of virtio pci device").
> > >
> > > Virtio drivers and PCI devices have never fully supported true
> > > surprise (aka hot
> > > unplug) removal. Drivers historically continued processing and waiting
> > > for pending I/O and even continued synchronous device reset during
> > > surprise removal. Devices have also continued completing I/Os, doing
> > > DMA and allowing device reset after surprise removal to support such drivers.
> > >
> > > Supporting it correctly would require a new device capability and
> > > driver negotiation in the virtio specification to safely stop I/O and free queue
> > memory.
> > > Failure to do so either breaks all the existing drivers with call
> > > trace listed in the commit or crashes the host on continuing the DMA.
> > > Hence, until such specification and devices are invented, restore the
> > > previous behavior of treating surprise removal as graceful removal to
> > > avoid regressions and maintain system stability same as before the
> > > commit 43bb40c5b926 ("virtio_pci: Support surprise removal of virtio pci
> > device").
> > >
> > > As explained above, previous analysis of solving this only in driver
> > > was incomplete and non-reliable at [1] and at [2]; Hence reverting
> > > commit
> > > 43bb40c5b926 ("virtio_pci: Support surprise removal of virtio pci
> > > device") is still the best stand to restore failures of virtio net and block
> > devices.
> > >
> > > [1]
> > >
> > https://lore.kernel.org/virtualization/CY8PR12MB719506CC5613EB100BC6C6
> > > 38 DCBD2@CY8PR12MB7195.namprd12.prod.outlook.com/#t
> > > [2]
> > > https://lore.kernel.org/virtualization/20250602024358.57114-1-parav@nv
> > > idia.c
> > > om/
> > >
> > > Fixes: 43bb40c5b926 ("virtio_pci: Support surprise removal of virtio
> > > pci device")
> > > Cc: stable@vger.kernel.org
> > > Reported-by: lirongqing@baidu.com
> > > Closes:
> > > https://lore.kernel.org/virtualization/c45dd68698cd47238c55fb73ca9b474
> > > 1@b
> > > aidu.com/
> > > Signed-off-by: Parav Pandit <parav@nvidia.com>
> > 
> > 
> > 
> > Tested-by: Li RongQing <lirongqing@baidu.com>
> > 
> > Thanks
> > 
> > -Li
> >
> Multiple users are blocked to have this fix in stable kernel.

what are these users doing that is blocked by this fix?

-- 
MST