lkml.org 
[lkml]   [2008]   [Aug]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86: split e820 reserved entries record to late v4


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


\
 
 \ /
  Last update: 2008-08-29 17:35    [W:0.068 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site