Re: Permissive devices in Xen

[Keir Fraser <keir@xensource.com>]

On 8/7/07 11:00, "Lukas Hejtmanek" <xhejtman@ics.muni.cz> wrote:

>> domU is not trusted to manage the i/o address space. We assume dom0 has set
>> up the values sanely and domU should have no reason to change them.
> 
> OK, I see. But there is problem with, e.g., InfiniBand card that during
> initialization performs reset of the card. The reset destroys the PCI config
> space therefore the driver reads 16 dwords from the config space and after
> reset, it writes them back. In DomU, it obviously does not restore address
> bars and the device fails to respond via MMIO.
> 
> So, I've tried to allow DomU (via pciback driver) to write also the address
> bars but in this case, I'm facing to huge SLAB corruptions. In Dom0 or non-Xen
> kernel, it works pretty well.
> 
> Do you have any hints how to track it down?

This was tracked down by Alex Williamson some time ago. There is code in
drivers/xen/pciback/conf_space_capability_pm.c:pm_ctrl_write() to restore
bars after a D3->D0 transition. I guess either your kernel does not have
that fix, or the fix needs to be extended slightly to cover whatever case
you are seeing.

 -- Keir