Re: [Xen-devel] [PATCH resend] xen-netback: switch to threaded irq for control ring

[Juergen Gross <jgross@xxxxxxxx>]

On 22/09/16 12:31, Paul Durrant wrote:
>> -----Original Message-----
>> From: Juergen Gross [mailto:jgross@xxxxxxxx]
>> Sent: 22 September 2016 11:17
>> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx;
>> netdev@xxxxxxxxxxxxxxxx <netdev@xxxxxxxxxxxxxxx>; linux-
>> kernel@xxxxxxxxxxxxxxx
>> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
>> Subject: Re: [Xen-devel] [PATCH resend] xen-netback: switch to threaded irq
>> for control ring
>>
>> On 22/09/16 11:09, Paul Durrant wrote:
>>>> -----Original Message-----
>>>> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of
>>>> Juergen Gross
>>>> Sent: 22 September 2016 10:03
>>>> To: xen-devel@xxxxxxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxxx; linux-
>>>> kernel@xxxxxxxxxxxxxxx
>>>> Cc: Juergen Gross <jgross@xxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>
>>>> Subject: [Xen-devel] [PATCH resend] xen-netback: switch to threaded
>>>> irq for control ring
>>>>
>>>> Instead of open coding it use the threaded irq mechanism in xen-netback.
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>>
>>> How have you tested this change?
>>
>> Only compile-tested and loaded the module. As this feature isn't being used
>> in linux netfront AFAIK it is not easily testable. OTOH the code 
>> modification is
>> rather limited and I've used the threaded irq in the Xen scsiback driver
>> myself, so I'm rather confident it will work.
>>
> 
> OK. How about doing the rx interrupt/task too so that it can be easily tested 
> with a linux netfront?

I'd like to, but this would require some more work. The rx kthread isn't
activated by an event only, but by a timer, too. This isn't easy to map
to the threaded irq framework. If, however, you are confident the timer
isn't really necessary I'd be happy to provide a patch switching the
rx task to the threaded irq, too.

And to be honest: this wouldn't verify that the control ring related
patch is really working. The mechanism itself _is_ working as it is
already in use in xen-scsiback in a very similar environment.


Juergen

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