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Re: [Xen-devel] [PATCHv1] xen/events/fifo: Handle linked events when closing a PIRQ port



On 08/10/2015 01:16 PM, David Vrabel wrote:
On 10/08/15 17:47, linux@xxxxxxxxxxxxxx wrote:
On 2015-08-10 16:24, David Vrabel wrote:
Commit fcdf31a7c162de0c93a2bee51df4688ab0a348f8 (xen/events/fifo:
Handle linked events when closing a port) did not handle closing a
port bound to a PIRQ because these are closed from shutdown_pirq()
which is called with interrupts disabled.

Defer the close to a work queue where we can safely spin waiting for
the LINKED bit to clear.  For simplicity, the close is always deferred
even if it is not required (i.e., we're already in process context).

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
Cc: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
Hi David,

Tested your patch, don't know for sure but this doesn't seem to work out.
I end up with this event channel error on dom0 boot.

Which ends in state:
Name                                        ID   Mem VCPUs    State
Time(s)
(null)                                       0  1536     6     r-----
  183.8

--
Sander

(XEN) [2015-08-10 16:35:34.584] PCI add device 0000:0d:00.0
(XEN) [2015-08-10 16:35:34.891] PCI add device 0000:0c:00.0
(XEN) [2015-08-10 16:35:35.123] PCI add device 0000:0b:00.0
(XEN) [2015-08-10 16:35:35.325] PCI add device 0000:0a:00.0
(XEN) [2015-08-10 16:35:35.574] PCI add device 0000:09:00.0
(XEN) [2015-08-10 16:35:35.642] PCI add device 0000:09:00.1
(XEN) [2015-08-10 16:35:35.872] PCI add device 0000:05:00.0
(XEN) [2015-08-10 16:35:36.044] PCI add device 0000:06:01.0
(XEN) [2015-08-10 16:35:36.109] PCI add device 0000:06:02.0
(XEN) [2015-08-10 16:35:36.293] PCI add device 0000:08:00.0
(XEN) [2015-08-10 16:35:36.603] PCI add device 0000:07:00.0
(XEN) [2015-08-10 16:35:36.906] PCI add device 0000:04:00.0
(XEN) [2015-08-10 16:35:37.074] PCI add device 0000:03:06.0
(XEN) [2015-08-10 16:35:39.456] PCI: Using MCFG for segment 0000 bus 00-ff
(XEN) [2015-08-10 16:35:49.623] d0: Forcing read-only access to MFN fed00
(XEN) [2015-08-10 16:35:51.374] event_channel.c:472:d0v0 EVTCHNOP
failure: error -17
This didn't happen on the test box I used but I can see it is possible
to rebind a PIRQ whose close is still deferred.

I'm going to revert fcdf31a7c162de0c93a2bee51df4688ab0a348f8
(xen/events/fifo: Handle linked events when closing a port) for now.


Any updates on these two patches? We started seeing this problem (stale events) in our testing when onlining/offlining vcpus in heavily oversubscribed guests.

-boris



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