[SeaBIOS] [PATCH] [Seabios] Over 4GB address ranges for 64bit PCI BARs
yamahata at valinux.co.jp
Mon Nov 8 05:11:02 CET 2010
On Mon, Nov 08, 2010 at 04:35:38PM +1300, Alexey Korolev wrote:
> > - >4GB 64bit bar allocation
> > Your patche tries to address this issue. But it breaks PCI-to-PCI
> > bridge filtering support.
> Hmm, it is quite possible, as we don't know a lot about seabios PCI-to-PCI bridge filtering support.
> Just out of curiosity: what is the issue?
It's pci_bios_init_device_bridge() in pciinit.c.
The function touches pci_bios_io_addr, pci_bios_mem_addr, and
So we need to modify, not only pci_bios_allocate_region(),
but also pci_bios_init_device_bridge().
The function programs the P2P bridge to forward IO/memory access
on primary pci bus to secondary pci bus.
It needs to be aware of 64bit BAR allocation.
> > If the BAR size is huge (or there are too many BARs), the bar can't
> > be allocated under 4G. So several persons want seabios to allocate
> > such BARs at >4GB area complaining that OS can't use BARs that seabios
> > didn't assigned.
> > Others think such BAR can be left unallocated.
> > Seabios role is to setup minimal basic environment for bootloader
> > to boot OS, 64bit bar allocation is beyond it's role.
> > bootloader/rombios usually doesn't handle BARs that is allocated
> > beyond 4GB, and Modern OSes can re-arrange PCI bar allocation itself.
> > So 64bit bar allocation support wouldn't be needed.
> > I'm not sure if there is enough demand to support 64bit BAR allocation
> > and if Kevin will accept it or not. Consensus is needed.
> > What OS are you using?
> For us >4GB allocation is welcome but not critical, because we mainly
> use Linux versions 2.6.18 and newer. We've tested the seabios without
> assignment of the regions which do not fit in first 32bit and it appears
> to work fine. So for us 64bit bar allocation support wouldn't be needed.
> It is possible that people will use an ancient version of Linux, but the
> probability of this event is very low.
My position is same to yours. Welcome, but not critical.
So the issue is, who will finish it.
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