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Re: [PATCH v3 2/8] xen/events: don't unmask an event channel when an eoi is pending
On 23.02.21 10:26, Ross Lagerwall wrote:
On 2021-02-19 15:40, Juergen Gross wrote:
An event channel should be kept masked when an eoi is pending for it.
When being migrated to another cpu it might be unmasked, though.
In order to avoid this keep three different flags for each event channel
to be able to distinguish "normal" masking/unmasking from eoi related
masking/unmasking and temporary masking. The event channel should only
be able to generate an interrupt if all flags are cleared.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 54c9de89895e0a36047 ("xen/events: add a new late EOI evtchn framework")
Reported-by: Julien Grall <julien@xxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
I tested this patch series backported to a 4.19 kernel and found that
when doing a reboot loop of Windows with PV drivers, occasionally it will
end up in a state with some event channels pending and masked in dom0
which breaks networking in the guest.
The issue seems to have been introduced with this patch, though at first
glance it appears correct. I haven't yet looked into why it is happening.
Have you seen anything like this with this patch?
Sorry it took so long, but now I was able to look into this issue.
I have managed to reproduce it with a pv Linux guest. I'm now adding
some debug code to understand what is happening there.
Juergen
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