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Re: [Xen-devel][PATCH] xen/netfront: Remove unneeded .resume callback




I am still confused about suspend/resume for the front drivers,
for instance, block front [1] does implement full/proper reconnect
on .resume, but net front only does this partially.

Could anyone please shed some light on suspend/resume design?

Thank you,
Oleksandr

On 3/14/19 3:17 PM, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

Currently on driver resume we remove all the network queues and
destroy shared Tx/Rx rings leaving the driver in its current state
and never signaling the backend of this frontend's state change.
This leads to the number of consequences:
- when frontend withdraws granted references to the rings etc. it cannot
   be cleanly done as the backend still holds those (it was not told to
   free the resources)
- it is not possible to resume driver operation as all the communication
   means with the backned were destroyed by the frontend, thus
   making the frontend appear to the guest OS as functional, but
   not really.

Fix this by not destroying communication channels/rings on driver
resume.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
---
  drivers/net/xen-netfront.c | 17 -----------------
  1 file changed, 17 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index c914c24f880b..2ca162048da4 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1422,22 +1422,6 @@ static void xennet_disconnect_backend(struct netfront_info *info)
  	}
  }
-/**
- * We are reconnecting to the backend, due to a suspend/resume, or a backend
- * driver restart.  We tear down our netif structure and recreate it, but
- * leave the device-layer structures intact so that this is transparent to the
- * rest of the kernel.
- */
-static int netfront_resume(struct xenbus_device *dev)
-{
-	struct netfront_info *info = dev_get_drvdata(&dev->dev);
-
-	dev_dbg(&dev->dev, "%s\n", dev->nodename);
-
-	xennet_disconnect_backend(info);
-	return 0;
-}
-
  static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[])
  {
  	char *s, *e, *macstr;
@@ -2185,7 +2169,6 @@ static struct xenbus_driver netfront_driver = {
  	.ids = netfront_ids,
  	.probe = netfront_probe,
  	.remove = xennet_remove,
-	.resume = netfront_resume,
  	.otherend_changed = netback_changed,
  };

[1] https://elixir.bootlin.com/linux/v5.0.2/source/drivers/block/xen-blkfront.c#L2072