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Re: [Xen-devel] [PATCHv1 net] xen-netback: support frontends without feature-rx-notify again

On 18/12/14 17:50, David Miller wrote:
> From: David Vrabel <david.vrabel@xxxxxxxxxx>
> Date: Thu, 18 Dec 2014 11:13:06 +0000
>> Commit bc96f648df1bbc2729abbb84513cf4f64273a1f1 (xen-netback: make
>> feature-rx-notify mandatory) incorrectly assumed that there were no
>> frontends in use that did not support this feature.  But the frontend
>> driver in MiniOS does not and since this is used by (qemu) stubdoms,
>> these stopped working.
>> Netback sort of works as-is in this mode except:
>> - If there are no Rx requests and the internal Rx queue fills, only
>>   the drain timeout will wake the thread.  The default drain timeout
>>   of 10 s would give unacceptable pauses.
>> - If an Rx stall was detected and the internal Rx queue is drained,
>>   then the Rx thread would never wake.
>> Handle these two cases (when feature-rx-notify is disabled) by:
>> - Reducing the drain timeout to 30 ms.
>> - Disabling Rx stall detection.
>> Reported-by: John <jw@xxxxxxxxxxxxxxxxxx>
>> Tested-by: John <jw@xxxxxxxxxxxxxxxxxx>
>> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> Applied, and I assume that 3.18 -stable needs this as well?

Yes, please.  Without it, netback just doesn't work with an important
use case.



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