Re: [PATCH] xen: don't use PCI BIOS service for configuration space accesses

[David Vrabel <david.vrabel@citrix.com>]

On 13/04/12 15:15, Jan Beulich wrote:
>>>> On 13.04.12 at 14:55, David Vrabel <david.vrabel@citrix.com> wrote:
>> On 13/04/12 13:29, Jan Beulich wrote:
>>>>>> On 13.04.12 at 14:08, David Vrabel <david.vrabel@citrix.com> wrote:
>>>> From: David Vrabel <david.vrabel@citrix.com>
>>>>
>>>> The accessing PCI configuration space with the PCI BIOS service does
>>>> not work in PV guests.
>>>>
>>>> This fixes boot on systems without MMCONFIG or where the BIOS hasn't
>>>> marked the MMCONFIG region as reserved in the e820 map.
>>>
>>> ... and where "direct" access doesn't work either? Are there really
>>> machines where Xen works on but this doesn't work? (Or, in case
>>> this is disabled in your config, is it really useful to have
>>> CONFIG_PCI_DIRECT disabled?)
>>
>> If you have CONFIG_PCI_GOANY (the default) BIOS is preferred over
>> direct.  So this change makes it skip BIOS and fall back to direct.
> 
> How is that? When I look at pci_arch_init(), I see pci_direct_probe()
> being called first.

Hmm. Direct /is/ preferred over BIOS.  But the BIOS is initialized even
if direct is eventually used and it's the init of the BIOS that dies.

I'll fixup the description to make this clearer.

David