Re: [Xen-devel] [edk2] Passing Xen memory map and resource map to OVMF

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Nov 14, 2013 at 08:58:18AM +0100, Gerd Hoffmann wrote:
>   Hi,
> 
> > > > OVMF
> > > > should just use whatever it gets.
> > > 
> > > What would OVMF use them for?
> > > 
> > 
> > To reserve range for MMIO holes, so that later PCI resource allocation
> > protocol can only use those ranges.
> 
> I'm still not convinced you need that in the first place.
> 
> When booting seabios @ xen it is not needed.  pci ressource allocation
> is handled by hvmloader.  apci tables (and the ressources declared
> therein) are handled by hvmloader.  seabios doesn't touch the pci bars
> and passes through the apci tables -> guest os is happy.
> 
> So why ovmf should be different?   IMHO it should operate like seabios
> and NOT do pci ressource allocation when running on xen.  Ressources are
> already handled already by hvmloader.  Doing it again is (a) pointless
> and (b) creates problems like the one we are discussion right now.
> 

Agreed. But the protocol to allocate PCI resources seems to be mandatory
according to UEFI spec [0].

--- page 16
The following protocols are mandatory if the system supports PCI devices
or slots: 
â EFI_PCI_HOST_BRIDGE_RESOURCE_ALLOCATION_PROTOCOL 
â EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL 
--

I'm more than happy to disable that allocation protocol if there's a way.

Wei.

[0] 
http://www.intel.com/content/dam/doc/reference-guide/efi-pci-host-bridge-allocation-protocol-specification.pdf

> cheers,
>   Gerd
> 

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