Messages in this thread | | | Date | Fri, 29 Aug 2008 08:31:08 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] x86: split e820 reserved entries record to late v4 |
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On Fri, 29 Aug 2008, Ingo Molnar wrote: > > > > you will get > > fec00000 - ffffffff reserved > > fed0000 - fed003ff hpet > > fed0000 - fed003ff 0000:00:14.0 > > ok - because it's fully contained insert_resource() will succeed?
Correct.
> I thought it would only succeed if the new resource was smaller than (a > subset of) the existing resource.
No, that's "request_resource()".
Yeah, I know, the resource code is complicated, and I wish it wasn't, but the whole issue with nesting resources correctly simply _is_ fairly complex.
So "insert_resource()" literally tries to fit a resource into an existing tree, at the right level, whatever level that is.
In contrast, "request_resource()" is about exclusivity, and tries to request a "leaf" resource - and it refuses to work if there are resources it clashes with that cover the same range.
> In the other direction, when a newly inserted resource is a superset of > the existing resource, i thought we'd fail.
For request_resource, yes.
> hypothetical scenario, what if we had neither a superset nor a subset > scenario, but a partial overlap, between: > > > > BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved) > > and: > > > > pci 0000:00:14.0: BAR has HPET at feb0f000-fec01000
Now THAT is somethign that the resource structs simply cannot handle. At that point you'd get a failure even from insert_resource(), because it no longer nests in the tree. You would have to split the range in order for it to nest properly.
Linus
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