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

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

On Fri, Nov 21, 2014 at 01:53:32PM -0300, Simon Martin wrote:
> Hello Konrad and Jan,
> 
> 
> > There was a bug in Xen pcibackend that I thought I upstreamed which could
> > be releated. It was not restoring the right registers to the PCI-device.
> 
> > They are attached.
> 
> Thanks for the patches, however I have been finding some very
> interesting things.
> 
> I decided to keep Xen out of the equation and booted into plain
> vanilla Linux. I then ran the FLR and got the same problem in the PCI
> configuration, all BARs were set to 0 and all reads to the PCI memory
> returned ff. I then manually wrote the correct values into the
> PCI BAR registers, and hey presto, reads to the PCI memory started
> working again!
> 
> Looks like my workaround for moment will be to store the PCI
> configuration registers before and resetting them after. Not cool, but
> something really strange is going on...

Right. Which is what the pciback does now (minus the bugs that the
two patches fix).

Look for pci_restore_config and pci_save_config
> 
> Thanks for your help.
> 
> Regards.
> 
> 
> -- 
> Best regards,
>  Simon                            mailto:furryfuttock@xxxxxxxxx
> 

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