From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christian Borntraeger <borntraeger@de.ibm.com>
Subject: Re: [virtio-dev] Re: [PATCH v2 0/4] virtio: Clean up scatterlists
	and use the DMA API
Date: Thu, 28 Aug 2014 21:18:46 +0200
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To: Andy Lutomirski <luto@amacapital.net>, Paolo Bonzini <pbonzini@redhat.com>
Cc: "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, "Michael S. Tsirkin" <mst@redhat.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Linux Virtualization <virtualization@lists.linux-foundation.org>, "linux390@de.ibm.com" <linux390@de.ibm.com>
List-ID: <linux-s390.vger.kernel.org>

On 28/08/14 21:03, Andy Lutomirski wrote:
> [removed virtio-dev -- I'm sick of bounces]
> 
> On Thu, Aug 28, 2014 at 11:55 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> Il 28/08/2014 20:29, Christian Borntraeger ha scritto:
>>>>>>> block seems to work, with net a simple ping works, iperf causes this:
>>>>>
>>>>> I neither see the bug, nor can I reproduce it on x86_64 on KVM.  I
>>>>> doubt that dma vs. non-dma is relevant.  I tried -net user a -net tap
>>>>> with iperf running in both directions.  I also tried switching
>>>>> virtio_pci into non-DMA-API mode.  No errors.
>>>>>
>>>>> Is there any chance that you could instrument that BUG_ON to print n,
>>>>> i, in_sgs, out_sgs, total_sg, total_in, and total_out?  I assume this
>>>>> is some oddity with patch 1, but I'm mystified.
>>> Yes, its triggered by patch 1.
>>
>> What version of QEMU?  Can you two cat the "features" file in the
>> virtio-net device's sysfs directory?
> 
> With vhost=on:
> 
> # cat /sys/class/net/eth0/device/features
> 0000011000000001111101010001110000000000000000000000000000000000
  > 
> Without vhost=on:
> 
> # cat /sys/class/net/eth0/device/features
> 0000011000000001111101010001110000000000000000000000000000000000
> 
> Instrumenting the code says that indirect=1.
> 
> --Andy
> 

I have 

1100011111111111111101010001110000000000000000000000000000000000