[coreboot] CBFS searches in Coreboot and SeaBIOS

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Sat Sep 26 02:41:40 CEST 2009

On 25.09.2009 20:04, Myles Watson wrote:
> On Fri, Sep 25, 2009 at 11:57 AM, Stefan Reinauer <stepan at coresystems.de>wrote:
>> But your reasons are very sound. It's quite a lot of cbfs accesses, and
>> generally I guess walking the device tree (in coreboot it's even a
>> memory op, and not a pci config space op) is cheaper than walking all of
>> the rom all of the time..
> It's not a show-stopper for me, but I thought I'd bring it up when I came to
> it.

Given that ages ago my proposal to add caching for LAR entries was
rejected (and I don't think positions have changed since then), LAR/CBFS
walking will stay somewhat expensive. You could build a special-case
cache of LAR entries for PCI option ROMs and hope nobody remembers the
original rejections. It would definitely speed up things a lot, while
saving you the trouble of changing the current option ROM init model.



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