Re: [Qemu-devel] [PATCH] pci: add standard bridge device

[Avi Kivity <avi@redhat.com>]

On 08/18/2011 10:12 PM, Wen Congyang wrote:
> >>
> >>  The following patch can fix this problem, but I'm not sure whether it
> >>  is right.
> >
> >  It's correct but insufficient, the filtering code (pci_bridge_filter)
> >  needs to be updated to use the memory API.
>
> I read the function pci_bridge_filter(), and the function only read
> PCI bridge's config space(command, base and limit). If base>  limit,
> it will set addr to PCI_BAR_UNMAPPED.
>
> I do not find anything that needs to updated to use the memory API.

Currently it doesn't do any filtering at all.  Bridges need to create a 
new address space, then attach aliases of this region (corresponding to 
the filtered area and to the legacy vga space) to the parent bus' 
address space.

> I add a scsi controller on pci bus1, and a scsi disk on this controller.
> I can read and write this disk, and I do not meet any problem.
>

However, filtering doesn't work.  You could put a BAR outside the 
filtered area and it would be visible to the guest.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.