linux-kernel - Re: [PATCH v4 2/3] xen/events: don't unmask an event channel when an eoi is pending

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Message-ID: <b6d41422-47cf-956c-9c4a-98998c64b103@citrix.com>
Date:   Tue, 9 Mar 2021 08:57:23 +0000
From:   Ross Lagerwall <ross.lagerwall@...rix.com>
To:     Jürgen Groß <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        <xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>
CC:     Stefano Stabellini <sstabellini@...nel.org>,
        <stable@...r.kernel.org>, Julien Grall <julien@....org>,
        Julien Grall <jgrall@...zon.com>
Subject: Re: [PATCH v4 2/3] xen/events: don't unmask an event channel when an
 eoi is pending

On 2021-03-09 05:14, Jürgen Groß wrote:
> On 08.03.21 21:33, Boris Ostrovsky wrote:
>>
>> On 3/6/21 11:18 AM, 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@...r.kernel.org
>>> Fixes: 54c9de89895e0a36047 ("xen/events: add a new late EOI evtchn framework")
>>> Reported-by: Julien Grall <julien@....org>
>>> Signed-off-by: Juergen Gross <jgross@...e.com>
>>> Reviewed-by: Julien Grall <jgrall@...zon.com>
>>> ---
>>> V2:
>>> - introduce a lock around masking/unmasking
>>> - merge patch 3 into this one (Jan Beulich)
>>> V4:
>>> - don't set eoi masking flag in lateeoi_mask_ack_dynirq()
>>
>>
>> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>>
>>
>> Ross, are you planning to test this?
> 
> Just as another data point: With the previous version of the patches
> a reboot loop of a guest needed max 33 reboots to loose network in
> my tests (those were IIRC 6 test runs). With this patch version I
> stopped the test after about 1300 reboots without having seen any
> problems.
> 

Thanks, I'll test it today and get back to you.

Ross