Re: [Xen-devel] [BUG] pci: mixed allocation pf and non-pf PCI MEM BAR (OVMF crash)

[Martin Cerveny <martin@xxxxxxxxx>]

Hello.

On Mon, 1 Apr 2019, Jan Beulich wrote:
> > > > On 31.03.19 at 10:11, <martin@xxxxxxxxx> wrote:
> > There is problem in PCI device allocation algorithm (pci_setup()).
> > Algorithm allocates PCI BAR sorted by size and this allows
> > mixed allocation of prefetchable and non-prefetchable PCI MEM BAR.
> > This leads to wrong config of PCI root port (see "Type 1 Configuration
> > Space Registers (Root Ports)").
> >
> > Tested with version xen 4.11.1 + "export
> > OVMF_UPSTREAM_REVISION=ef529e6ab7c31290a33045bb1f1837447cc0eb56"
> > (embeded commit OVMF does not work (crashed even in Win10.iso and
> > uncompilable with newer gcc)).
> >
> > Attached also testing patch.
> I agree the problem wants addressing, but I'm afraid the patch is
> incomplete: Afaict it won't work if there is a non-prefetchable BAR
> larger than the smallest prefetchable one, due to the necessary
> extra padding that would need inserting between the two.
I make this patch as proof-of-concept to get it compatible 
with OVMF. But I am not aware if OVMF is OK and all other consequences, like:
- allocation aligning as you mention
- PF region to be placed first or last in MMIO hole 
- some PCI express documents says that all 64bit MEM BAR must be prefetchable
[ But if I activate "usbversion=3" it generates 64bit MEM BAR but without 
prefetchable bit (so PCI_BASE_ADDRESS_MEM_PREFETCH is implicit?) and 
actual code allocates MMIO under 4G. But OVMF requires that 64bit MEM BAR 
must be placed over 4G (just another problem/BUG). ]
(example - 
https://resources.infosecinstitute.com/system-address-map-initialization-x86x64-architecture-part-2-pci-express-based-systems/
 )

> Also the patch lack your S-o-b and has a couple of style issues
> (hard tab used, indentation, lack of blanks inside if(), unnecessary
> double use of PCI_BASE_ADDRESS_MEM_PREFETCH).
> As to its description - do you perhaps mean "interleaved" instead
> of "fragmented" and "not allowed" instead of "not supported"?
Rework/use the patch as needed.

Martin

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