netdev - Re: [Xen-devel] [RFC 21/23] net/xen-netback: Make it running on 64KB page granularity

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Date:	Wed, 20 May 2015 15:29:19 +0100
From:	Julien Grall <julien.grall@...rix.com>
To:	Julien Grall <julien.grall@...rix.com>,
	Wei Liu <wei.liu2@...rix.com>, <ian.campbell@...rix.com>
CC:	<stefano.stabellini@...citrix.com>, <netdev@...r.kernel.org>,
	<tim@....org>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xenproject.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Subject: Re: [Xen-devel] [RFC 21/23] net/xen-netback: Make it running on 64KB
 page granularity


On 19/05/15 23:56, Julien Grall wrote:
>> If you're wgetting from another host, I would suggest wgetting from Dom0
>> to limit the problem between Dom0 and DomU.
> 
> Thanks to Wei, I was able to narrow the problem. It looks like the
> problem is not coming from netback but somewhere else down in the
> network stack: wget/ssh between Dom0 64KB and DomU is working fine.
> 
> Although, wget/ssh between a guest and an external host doesn't work
> when Dom0 is using 64KB page granularity unless if I start a tcpdump on
> the vif in DOM0. Anyone an idea?
> 
> I have no issue to wget/ssh in DOM0 to an external host and the same
> kernel with 4KB page granularity (i.e same source code but rebuilt with
> 4KB) doesn't show any issue with wget/ssh in the guest.
> 
> This has been tested on AMD Seattle, the guest kernel is the same on
> every test (4KB page granularity).
> 
> I'm planning to give a try tomorrow on X-gene (ARM64 board and I think
> 64KB page granularity is supported) to see if I can reproduce the bug.

It's working on X-gene with the same kernel and configuration. I guess
we can deduce that it's a bug in the AMD network driver.

Regards,

-- 
Julien Grall
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