Re: PCI: disable I/O or mem before probing BAR size

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> while trying to boot a Xen PVH kernel as dom0, I found that Xen
> doesn't allow changing memory-mapped PCI BARs if memory decode is
> enabled in the command register.

Is this permitted behaviour for a PCI device according to the PCI
specs?  I'm just thinking that, if not, it's a bug in Xen and, while
NetBSD might want to work around it, the code to do so should make it a
lot clearer to code readers that it _is_ a bug workaround.  (If it _is_
permitted, it's pretty clearly a bug in NetBSD and needs fixing, of
course - and in that case there probably is a bunch more code that
needs fixing too; I've seen enough things that don't mess with decoding
enables before checking for decode width....)

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