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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.04.12 at 14:55, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
> On 13/04/12 13:29, Jan Beulich wrote:
>>>>> On 13.04.12 at 14:08, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
>>> From: David Vrabel <david.vrabel@xxxxxxxxxx>
>>>
>>> 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.

> On the system I had saw the problem, the first call into the BIOS
> service would hang the system.

Sure.

Jan


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