Re: [Xen-devel] PCI passthrough issue

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Jan 12, 2011 at 05:56:45PM +0100, Jean Baptiste Favre wrote:
> Le 12/01/2011 17:36, Konrad Rzeszutek Wilk a écrit :
> > On Wed, Jan 12, 2011 at 04:53:51PM +0100, Jean Baptiste Favre wrote:
> >> Hello Konrad,
> >>
> >> Le 12/01/2011 16:43, Konrad Rzeszutek Wilk a écrit :
> >>> On Wed, Jan 12, 2011 at 04:38:49PM +0100, Jean Baptiste Favre wrote:
> >>>> Hello,
> >>>> I'm facing a strange issue with network card PCI passthrough on my
> >>>> openwrt test domU.
> >>>>
> >>>> - With network PCI passthrough, DNS lookup failed for some domains
> >>>> (exemple, google.com) but not for other (free.fr my ISP, or my domain
> >>>> jbfavre.org). I can ping an IP address without any problem.
> >>>
> >>> Do you have "both" (so PCI passthrough and the Xen network driver)
> >>> in the guest? If so, have you tried eliminating the xen network driver
> >>> to see if it is just a routing issue?
> >> Have not tried to eliminate xen network driver. Think I have both drivers.
> >>
> >> My kernel .config looks like:
> >> $ grep XEN build_dir/linux-x86_xen_domu/linux-2.6.37/.config
> >> CONFIG_XEN=y
> >> # CONFIG_XEN_PRIVILEGED_GUEST is not set
> >> CONFIG_XEN_PVHVM=y
> >> CONFIG_XEN_MAX_DOMAIN_MEMORY=128
> >> CONFIG_XEN_SAVE_RESTORE=y
> >> CONFIG_PCI_XEN=y
> >> CONFIG_XEN_PCIDEV_FRONTEND=y
> >> CONFIG_XEN_BLKDEV_FRONTEND=y
> >> CONFIG_XEN_NETDEV_FRONTEND=y
> >> CONFIG_HVC_XEN=y
> >> CONFIG_XEN_BALLOON=y
> >> CONFIG_XEN_SCRUB_PAGES=y
> >> CONFIG_XEN_DEV_EVTCHN=y
> >> CONFIG_XENFS=y
> >> CONFIG_XEN_COMPAT_XENFS=y
> >> CONFIG_XEN_SYS_HYPERVISOR=y
> >> # CONFIG_XEN_PLATFORM_PCI is not set
> >> CONFIG_SWIOTLB_XEN=y
> >>
> >> So, I should remove CONFIG_XEN_NETDEV_FRONTEND ?
> > 
> > No. You can just do 'ifconfig <x> down' whatever your Xen netfront
> > NIC is. .. but.
> >>
> >>> What does your routing table look like? Your IP table?
> >> My routing table is pretty clean, nothing strange here
> >> # route -n
> >> Kernel IP routing table
> >> Destination     Gateway         Genmask         Flags Metric Ref    Use
> >> Iface
> >> 10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0
> >> br-wan
> >> 0.0.0.0         10.0.0.1        0.0.0.0         UG    0      0        0
> >> br-wan
> > 
> > Ok, then the idea that the Xen networking driver and the PCI passthrough 
> > send
> > packets over is not the way..
> > 
> > So ignore about the Xen networking part.
> 
> OK.
> 
> >>
> >>>> - Starting domU as a "normal" (ie without PCI passthrough), no problem.
> >>>>
> >>>>
> >>>> As far as I can say, domU is not the root cause. I really think this is
> >>>> related to PCI passsthrough. This seems to be related to packet length.
> >>>
> >>> Then that would imply the MTU is not set right. 
> >> Already checked it: 1500 :)
> > Ok.
> > 
> > Next thing, did you try to disable the rx/tx checksumming?
> 
> No. Not sure I even know how to do it, but will have a look on that.
> 
> > If you connect the Ethernet cable for this 'br-wan' device to another 
> > machine
> > (so you could set it up as bridge and just let it pass through packets and 
> > sniff
> > the data) what do the packets look like?
> 
> I can see packets on my gateway (which acts as DNS as well). They looks
> good. I can see DNS answers as well leaving the gateway, but not
> reaching my domU. Have only basic switches between my gateway and my domU.

Wait a minute. How are your domU's connected? You did turn on
forwarding in your guest with the PCI passthrough right?

How is your domain (with the PCI passthrought) connected to the
other domains?
> 
> > What happens if the PCI passthrough device is not under the ownership of a 
> > bridge?
> > What then? You wouldn't have any bridge firewall code in?
> 
> Removed bridge + configure eth: no change.
> Checked ebtables/iptables (all tables: net filter and mangle) rules:
> empty, Policy to ACCEPT.
> Tried to enable/disable ip_forwarding: no change
> Also disabled IPV6 support (I saw some DNS answers as AAAA but no IPv6
> available at home for now): no change
> 
> Regards,
> JB
> 
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