Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard resources

Jesse Barnes
2007-05-23T00:38:34Z

On Tuesday, May 22, 2007, Robert Hancock wrote:
> Eww. I don't see where we disable the decode at all while we probe the
> BARs on the device. That seems like a bad thing, especially with the way
> we probe 64-bit BARs (do the low 32 bits first and then the high 32
> bits). This means the base address effectively gets set to 0xfffffff0
> momentarily, which might cause some issues.

I'm a bit shocked that things work as well as they do without the
disabling...

> I'd try adding some code inside pci_setup_device (drivers/pci/probe.c)
> to disable PCI_COMMAND_IO and PCI_COMMAND_MEMORY on the device when
> probing devices with the standard header type and then restoring the
> previous command bits afterwards, and see what effect that has. It'll be
> interesting if it does, since obviously it seems to work as it is with
> non-MMCONFIG access methods. Maybe the base address being set like that
> interferes with MMCONFIG access itself somehow?

I tried that, and it seems to get past probing the graphics device at
least, but it hangs a bit later. It could be that the enable/disable I
added wasn't correct though, I didn't check to see which one I should
disable in the command word, which may be a problem (just disabled them
both every probe). I'll try again with more precise enable/disable
semantics.

Jesse