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Date:	Thu, 1 May 2014 16:05:13 +0200
From:	Sander Eikelenboom <>
To:	Zoltan Kiss <>
CC:	Ian Campbell <>,
	"David S. Miller" <>, <>,
Subject: Re: [3.15-rc3] Bisected: xen-netback mangles packets between two guests on a bridge since merge of "TX grant mapping with SKBTX_DEV_ZEROCOPY instead of copy" series.

Thursday, May 1, 2014, 3:49:45 PM, you wrote:

> On 30/04/14 11:45, Sander Eikelenboom wrote:
>>      Another point would be: what *correctness* testing is actually done on the xen-net* patches ?
> I can speak only about my patches: I have manually tested them for the 
> usecases where they likely to make a difference, plus they went through 
> Xenserver's full test suite several times.

I think Paul's patches for 3.14 also went through this testsuite fine, however 
it did have a bug in it. Does this testsuite include a test which causes a 
diverse pattern of frags (for both tx and rx case) ?

>>      As i suspect this is again about fragmented packets .. that doesn't seem to be included in any test case while it actually seems to be a case which is hard to get right...
> Beware, there are frags and frag_list which are two entirely different 
> things with confusing names. In netback case, frags are used to pass 
> through large packets for a long time. frag_list is used only since my 
> grant mapping patches, to handle older guests (see comment in 
> include/xen/interface/io/netif.h for XEN_NETIF_NR_SLOTS_MIN)

Ah ok .. it's not about the frags in the packets being handled, but the frag 
mechanism is supposed to be used internally ?

If so .. there is at least something wrong in the "older guest" detection,
because both dom0 and PV guests are running the same 3.15-rc3 kernel.

> Zoli

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