[SeaBIOS] [PATCH 0/5] pci: 64bit support

Gerd Hoffmann kraxel at redhat.com
Wed Feb 22 11:55:53 CET 2012


>> I haven't really had a chance to review it.  Initial thoughts were
>> - on patch 1, I'm not sure how that will impact stack usage which
>> is quite tight when running in 16bit mode;

Stack usage doesn't grow much I think.  struct pci_dev becomes larger,
but I doubt you can find those on the stack.  Some local variables move
from u32 to u64.  But doesn't run this code in 32bit anyway?

>> patch 5 - seems incomplete if it doesn't handle bridges properly.
>> I didn't fully understand patch 5, but that's likely just due to
>> lack of time to look at it.

Yea, 64bit window detection isn't there, couldn't test that because qemu
didn't support it, but mst posted a patch for that yesterday.

>> BTW, what's the use case for 64bit PCI today?
> Hmm at the moment I've almost complete testing of another
> implementation of 64bit BAR support. It's implemeted in a very
> different way. Just need a day or so to form patches and write a
> description.

Oh, ok.  I had the impression the effort is stalled due to complete
silence for a bunch of weeks.  /me looks forward to look at your patches.

> Who needs this today. At the moment qemu 1.0 does not work with 64bit
> BARs properly.

latest master works fine.

> If 64bit BAR support is implemented we will be able to go ahead with
> network monitoring card in qemu. So we need this feature.  In
> addition big memory ranges (i.e. 64bit BARs) are very desirable for
> qemu ivshmem driver (virtual pci device for inter-vm shared memory).
> And I'm pretty sure there will be other use cases.

Yea, this is pretty much about moving large memory bars out of the PCI
address space window below 4G.  ivshmem is a obvious candidate.  I have
patches for QXL too.


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