Re: [virtio-dev] Re: [PATCH v2 0/4] virtio: Clean up scatterlists and use the DMA API

Andy Lutomirski
2014-08-28T19:03:19Z

[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