Re: [Xen-devel] PCI passthrough issue

[Jean Baptiste Favre <xen-devel@xxxxxxxxxxx>]

Le 13/01/2011 21:19, Konrad Rzeszutek Wilk a écrit :
> On Thu, Jan 13, 2011 at 08:18:33PM +0100, Jean Baptiste Favre wrote:
>> Hello,
>> My dom0 is back and I performed some more tests.
>>
>> I told in my first mail that ping works. Indeed it works, but not always:
>> # ping -c2 10.0.0.1
>> PING 10.0.0.1 (10.0.0.1): 56 data bytes
>> 64 bytes from 10.0.0.1: seq=0 ttl=64 time=0.846 ms
>> 64 bytes from 10.0.0.1: seq=1 ttl=64 time=0.824 ms
>>
>> --- 10.0.0.1 ping statistics ---
>> 2 packets transmitted, 2 packets received, 0% packet loss
>> round-trip min/avg/max = 0.824/0.835/0.846 ms
>> # ping -c2 -s60 10.0.0.1
>> PING 10.0.0.1 (10.0.0.1): 60 data bytes
>> 68 bytes from 10.0.0.1: seq=0 ttl=64 time=0.819 ms
>> 68 bytes from 10.0.0.1: seq=1 ttl=64 time=0.807 ms
>>
>> --- 10.0.0.1 ping statistics ---
>> 2 packets transmitted, 2 packets received, 0% packet loss
>> round-trip min/avg/max = 0.807/0.813/0.819 ms
>>
>> Increasing packet size is ok until this one:
>> # ping -c2 -s85 10.0.0.1
>> PING 10.0.0.1 (10.0.0.1): 85 data bytes
>> 93 bytes from 10.0.0.1: seq=0 ttl=64 time=0.823 ms
>> 93 bytes from 10.0.0.1: seq=1 ttl=64 time=0.816 ms
>>
>> --- 10.0.0.1 ping statistics ---
>> 2 packets transmitted, 2 packets received, 0% packet loss
>> round-trip min/avg/max = 0.816/0.819/0.823 ms
>> root@OpenWrt:/# ping -c2 -s86 10.0.0.1
>> PING 10.0.0.1 (10.0.0.1): 86 data bytes
>>
>> --- 10.0.0.1 ping statistics ---
>> 2 packets transmitted, 0 packets received, 100% packet loss
>>
>> As you see, packet size seems to be limited in a way. From another
>> machine on the same LAN I can do ping -s1500 without any problem.
> 
> One thing that I just thought (which I keep on forgetting to do).
> You did set 'iommu=soft' in your Linux guest, right?

Tought I told it in my previou smails. Sorry to missed it:

On my dom0:
$ cat /proc/cmdline
placeholder root=/dev/mapper/system-root ro console=hvc0 earlyprintk=xen
nomodeset xen-pciback.permissive xen-pciback.hide=(04:00.0)
pci=resource_alignment=04:00.0 quiet

Xen hypervisor options are:
# xm dmesg
(XEN) Xen version 4.0.1 (Debian 4.0.1-1) (waldi@xxxxxxxxxx) (gcc version
4.4.5 20100824 (prerelease) (Debian 4.4.4-11) ) Fri Sep  3 15:38:12 UTC 2010
(XEN) Bootloader: GRUB 1.98+20100804-11
(XEN) Command line: placeholder dom0_mem=256M dom0_max_vcpus=1
dom0_vcpus_pin loglvl=all guest_loglvl=all com1=115200,8n1 console=com1

OpenWRT domU config file is:
$ cat /etc/xen/auto/openwrt.cfg

kernel       = '/home/domU/wrt/openwrt-x86-xen_domu-vmlinuz'
root         = '/dev/xvda2 rw'
memory       = '256'
vcpus        = '1'
cpus         = '1'
localtime    = 0
serial       = 'pty'
disk = ['file:/home/domU/wrt/openwrt-x86-xen_domu-combined-ext4.img,xvda,w']

#vif = [ 'bridge=br-wan, mac=00:16:3E:01:00:64, vifname=wrt-100.eth1' ]

on_poweroff  = 'destroy'
on_reboot    = 'restart'
on_crash     = 'restart'

extra = "iommu=soft swiotlb=force console=hvc0 xencons=tty"
pci = [ '04:00.0' ]

name         = 'openwrt'
hostname     = 'openwrt.clichy.jbfavre.org'


>> So I think I hit a bug. Either it's Xen related, or Debian (through
>> debian kernel version). Now the question is: how can I determine which
>> part is responsible ?
> 
> What does tcpdump tell you when you try to send it at -s86?

I can see echo requests coming in on my gateway, replies going back but
replies are never received on the domU.

Regards,
JB

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