Re: [Xen-devel] Problems accessing passthrough PCI device

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.11.14 at 16:12, <furryfuttock@xxxxxxxxx> wrote:
> This   is  getting  more  interesting.  It  seems  that  something  is
> overwriting the pci-back configuration data.
> 
> Starting  from a fresh reboot I checked the Dom0 pci configuration and
> got this:
> 
> root@smartin-xen:~# lspci -s 00:19.0 -x
> 00:19.0 Ethernet controller: Intel Corporation Device 1559 (rev 04)
> 00: 86 80 59 15 00 00 10 00 04 00 00 02 00 00 00 00
> 10: 00 00 d0 f7 00 c0 d3 f7 81 f0 00 00 00 00 00 00
> 20: 00 00 00 00 00 00 00 00 00 00 00 00 86 80 54 20
> 30: 00 00 00 00 c8 00 00 00 00 00 00 00 05 01 00 00
> 
> I then start/stop my DomU and checked the Dom0 pci configuration again
> and got this:
> 
> root@smartin-xen:~# lspci -s 00:19.0 -x
> 00:19.0 Ethernet controller: Intel Corporation Device 1559 (rev 04)
> 00: 86 80 59 15 00 00 10 00 04 00 00 02 00 00 00 00
> 10: 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00
> 20: 00 00 00 00 00 00 00 00 00 00 00 00 86 80 54 20
> 30: 00 00 00 00 c8 00 00 00 00 00 00 00 05 01 00 00

I.e. the BARs got zapped. Not something that should happen. And
certainly explaining why you would not be able to use the device a
second time.

> Inside  my  DomU I added code to print the PCI configuration registers
> and what I get after restarting the DomU is:
> 
> (d18) 14:57:04.042 src/e1000e.c@00150: 00: 86 80 59 15 00 00 10 00 04 00 00 
> 02 00 00 00 00
> (d18) 14:57:04.042 src/e1000e.c@00150: 10: 00 00 d0 f7 00 c0 d3 f7 81 f0 00 
> 00 00 00 00 00
> (d18) 14:57:04.042 src/e1000e.c@00150: 20: 00 00 00 00 00 00 00 00 00 00 00 
> 00 86 80 54 20
> (d18) 14:57:04.043 src/e1000e.c@00150: 30: 00 00 00 00 c8 00 00 00 00 00 00 
> 00 14 01 00 00
> (d18) 14:57:04.043 src/e1000e.c@00324: Enable PCI Memory Access
> (d18) 14:57:05.043 src/e1000e.c@00150: 00: 86 80 59 15 03 00 10 00 04 00 00 
> 02 00 00 00 00
> (d18) 14:57:05.044 src/e1000e.c@00150: 10: 00 00 d0 f7 00 c0 d3 f7 81 f0 00  
> 00 00 00 00 00
> (d18) 14:57:05.044 src/e1000e.c@00150: 20: 00 00 00 00 00 00 00 00 00 00 00 
> 00 86 80 54 20
> (d18) 14:57:05.045 src/e1000e.c@00150: 30: 00 00 00 00 c8 00 00 00 00 00 00 
> 00 14 01 00 00
> 
> As  you can see the pci configuration read from the pci-back driver by
> my DomU is different to the data in the Dom0 pci configuration!

The only byte that is different afaics is the one at 0x3c, and that's
fine. Plus comparing with what Dom0 sees before the guest was
started or after the guest was stopped isn't really meaningful -
instead you'd want to compare against what Dom0 sees while the
guest is running.

But in the end your problem may have to do with the various
warnings issued regarding unrecognized DMAR table data, all
relating to the use of namespaces that our code doesn't have
support for.

Jan


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