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

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Date:   Tue, 9 Mar 2021 06:14:14 +0100
From:   Jürgen Groß <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        ross.lagerwall@...rix.com
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 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.

Juergen

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