[Pkg-xen-devel] Problems with PCI pass-through

[Pasi Kärkkäinen]

On Fri, May 28, 2010 at 11:18:56PM +0200, Thomas Schwinge wrote:
> Hello!
> 
> I'm having problems getting PCI pass-through to work.
> 
> This is on a AMD64 system, paravirtualized with xen-hypervisor-4.0-amd64
> 4.0.0-1~experimental.1, dom0: linux-image-2.6.32-5-xen-amd64 2.6.32-12.
> 

Can you try grabbing a kernel from Jeremy's xen.git xen/stable-2.6.32.x branch
and compiling it.. ? 
 
Just yesterday there was an user on ##xen telling it worked OK for him.
Other than that.. dunno really.

What's the Xen PCI backend mode on dom0 kernel .config? 

-- Pasi

> From IRC, earlier today:
> 
> <tschwinge> waldi: Aren't the Debian xen domU-capable kernels supposed to
>   contain the PCI frontend (needed for PCI pass-through)?  I'm getting:
>   PCI: System does not support PCI
> <tschwinge> waldi: ... both when using linux-image-2.6.32-3-686-bigmem
>   and linux-image-2.6.32-5-xen-686 for the domU.
> <tschwinge> Hrm.
>   /boot/config-2.6.32-5-xen-686:CONFIG_XEN_PCIDEV_FRONTEND=y
> 
> So, yes for that one, and no for the 686-bigmem one -- which is also what
> is said on
> <http://wiki.xensource.com/xenwiki/XenKernelFeatures#head-9df801d47f748067dc67b71979905a00f9e3cef9>.
> 
> <tschwinge> Why doesn't think work then?
> <tschwinge> xm pci-list-assignable-devices
> <tschwinge> ... does show the device.
> <tschwinge> If I start the domU, xm pci-list domU doesn show it, too.
> <tschwinge> But then:
> <tschwinge> kepler:~# dmesg | grep -i pci
> <tschwinge> [    0.000000] Allocating PCI resources starting at 1c800000 (gap: 1c800000:e3800000)
> <tschwinge> [    0.010467] PCI: setting up Xen PCI frontend stub
> <tschwinge> [    0.020145] PCI: System does not support PCI
> <tschwinge> [    0.020160] PCI: System does not support PCI
> <tschwinge> [    0.204967] pcifront pci-0: Installing PCI frontend
> <tschwinge> [    0.205093] pcifront pci-0: Creating PCI Frontend Bus 0000:00
> <tschwinge> ... and lspci doesn't show anything.
> <bwh^> That kernel seems... confused
> <bwh^> OK, the two 'System does not support PCI' messages come from the
>   PCIBIOS and PCI legacy probe code
> <tschwinge> bwh^: So, any idea what might be wrong for me?
> <bwh^> Not a lot
> <bwh^> but those warnings can be ignored (and should really be improved)
> 
> In contrast to that:
> 
> <tschwinge> If I boot with the old pre-pvops 2.6.26-2-xen-686 kernel, I
>   do see the PCI device with lspci: 00:00.7 Multimedia audio controller:
>   Silicon Integrated Systems [SiS] AC'97 Sound Controller (rev a0)
> <tschwinge> And dmesg is mostly the same:
> <tschwinge> dmesg | grep -i pci
> <tschwinge> [    0.000000] Allocating PCI resources starting at 20000000 (gap: 1d000000:e3000000)
> <tschwinge> [    0.333116] PCI: Fatal: No config space access function found
> <tschwinge> [    0.333133] PCI: setting up Xen PCI frontend stub
> <tschwinge> [    0.353896] PCI: System does not support PCI
> <tschwinge> [    0.353911] PCI: System does not support PCI
> <tschwinge> [    0.401513] pcifront pci-0: Installing PCI frontend
> <tschwinge> [    0.401609] pcifront pci-0: Creating PCI Frontend Bus 0000:00
> <tschwinge> Yet, staying with that kernel won't be the solution.  :-)
> <bwh^> tschwinge: No indeed
> 
> If I use the ``iommu=soft swiotlb=force'' switches as given on
> <http://wiki.xensource.com/xenwiki/XenPCIpassthrough>, nothing changes,
> apart from an additional ``PCI-DMA: Using software bounce buffering for
> IO (SWIOTLB)'' line in the dmesg.
> 
> Any ideas?
> 
> 
> Regards,
>  Thomas