Re: [Xen-devel] PCI passthrough issue

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

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 ?

> 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

>> - 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 :)

>> Did not see anything strange in dom0 logs.
>>
>> Is there any incompatibility between 2.6.32 dom0 kernel with Xen 4.0.1
>> and 2.6.37 domU kernel ?
> 
> No.
So, will try to remove Xen Network driver and see what happen.

Regards,
JB

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