Re: [Xen-devel] PCI passthrough issue

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

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.
> 
> >> - 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?

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?

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?

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