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From: "Jürgen Groß" <jgross@suse.com>
To: Ross Lagerwall <ross.lagerwall@citrix.com>,
	xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	stable@vger.kernel.org, Julien Grall <julien@xen.org>
Subject: Re: [PATCH v3 2/8] xen/events: don't unmask an event channel when an eoi is pending
Date: Fri, 5 Mar 2021 11:53:25 +0100	[thread overview]
Message-ID: <f0b1bd7d-d751-213a-ba13-b271fcee6403@suse.com> (raw)
In-Reply-To: <d368a948-17d6-4e64-110e-bede3158f49f@citrix.com>


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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@vger.kernel.org
>> Fixes: 54c9de89895e0a36047 ("xen/events: add a new late EOI evtchn framework")
>> Reported-by: Julien Grall <julien@xen.org>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
> 
> 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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  reply	other threads:[~2021-03-05 10:53 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-19 15:40 [PATCH v3 0/8] xen/events: bug fixes and some diagnostic aids Juergen Gross
2021-02-19 15:40 ` [PATCH v3 1/8] xen/events: reset affinity of 2-level event when tearing it down Juergen Gross
2021-02-19 15:40 ` [PATCH v3 2/8] xen/events: don't unmask an event channel when an eoi is pending Juergen Gross
2021-02-20 12:10   ` Julien Grall
2021-02-23  9:26   ` Ross Lagerwall
2021-03-05 10:53     ` Jürgen Groß [this message]
2021-03-06 16:18     ` Jürgen Groß
2021-02-19 15:40 ` [PATCH v3 3/8] xen/events: avoid handling the same event on two cpus at the same time Juergen Gross
2021-02-20 12:12   ` Julien Grall
2021-02-19 15:40 ` [PATCH v3 4/8] xen/netback: fix spurious event detection for common event case Juergen Gross
2021-02-19 15:40 ` [PATCH v3 5/8] xen/events: link interdomain events to associated xenbus device Juergen Gross
2021-02-22 14:50   ` Roger Pau Monné
2021-02-19 15:40 ` [PATCH v3 6/8] xen/events: add per-xenbus device event statistics and settings Juergen Gross
2021-02-19 15:40 ` [PATCH v3 7/8] xen/evtchn: use smp barriers for user event ring Juergen Gross
2021-02-19 15:40 ` [PATCH v3 8/8] xen/evtchn: use READ/WRITE_ONCE() for accessing ring indices Juergen Gross
2021-02-20 20:35   ` Boris Ostrovsky
2021-02-23 15:44 ` [PATCH v3 0/8] xen/events: bug fixes and some diagnostic aids Boris Ostrovsky

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