Re: Is: SKB_MAX_LEN bites again. Was: Re: bug disabling guest interface

Steven Haigh
Sat, 09 Mar 2013 02:19:40 -0000

On 9/03/2013 9:09 AM, Jacek Milewicz wrote:
>>>> Is there any further information on a possible fix for this?
> Thoughts?
>>>> Ideas? As it seems to be hitting multiple sites, I''d
like to get it
>>> fixed asap...
>>>
>>> There are 3 ways I can see this fixed:
>>> - update guests so all have same MAX_SKB_FRAGS (that includes
windows
>>> drivers (windows drivers use 19 for MAX_SKB_FRAGS)) -add some sort
of
>>> negotiation between host and guest
>>> - change MAX_SKB_FRAGS to 19 to accommodate all guests
>>>
>>> Unfortunately first one requires changes to the guest and most
don''t
>>> have that luxury. So the only way I see it could be fixed without
>>> breaking compatibility even more  is
>>
>> Ugh. The negotiations between host and guest is probably the best
> choice.
>> The issues you are going to hit are that you might need to redo the
skbs
> to
>> match what the frontend''s max is.
>>
>> Annie, Wei, Ian - were there some RFC patches floating around for this?
>>
>
> As much as I agree that negotiation is the best option in long term. It
> relies on people upgrading their kernels - and this is not the case (only
> people running kernels from before 2011-12-23 are affected by this bug
> (I''m not sure about other platforms)).
> And in a lot of cases (VPS providers) there is no easy way to upgrade
> guest kernels.

For what its worth, I''ve increased the value of MAX_SKB_FRAGS to 19 on
my Dom0 kernel and pushed out new packages... I''ll see if I get any
further reports...

--
Steven Haigh

Email: netwiz@crc.id.au
Web: https://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897
Fax: (03) 8338 0299



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