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

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> 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/CY8PR12MB719506CC5613EB100BC6C638
> DCBD2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/#t
> [2]
> https://lore.kernel.org/virtualization/20250602024358.57114-1-parav@nvidia.c
> om/
> 
> Fixes: 43bb40c5b926 ("virtio_pci: Support surprise removal of virtio pci device")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: lirongqing@xxxxxxxxx
> Closes:
> https://lore.kernel.org/virtualization/c45dd68698cd47238c55fb73ca9b4741@b
> aidu.com/
> Signed-off-by: Parav Pandit <parav@xxxxxxxxxx>



Tested-by: Li RongQing <lirongqing@xxxxxxxxx>

Thanks

-Li


> ---
>  drivers/virtio/virtio_pci_common.c | 7 -------
>  1 file changed, 7 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci_common.c
> b/drivers/virtio/virtio_pci_common.c
> index d6d79af44569..dba5eb2eaff9 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -747,13 +747,6 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
>  	struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
>  	struct device *dev = get_device(&vp_dev->vdev.dev);
> 
> -	/*
> -	 * Device is marked broken on surprise removal so that virtio upper
> -	 * layers can abort any ongoing operation.
> -	 */
> -	if (!pci_device_is_present(pci_dev))
> -		virtio_break_device(&vp_dev->vdev);
> -
>  	pci_disable_sriov(pci_dev);
> 
>  	unregister_virtio_device(&vp_dev->vdev);
> --
> 2.26.2






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