Messages in this thread | | | Date | Fri, 29 Aug 2008 09:28:33 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: split e820 reserved entries record to late v4 |
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* Yinghai Lu <yhlu.kernel@gmail.com> wrote:
> On Thu, Aug 28, 2008 at 11:58 PM, Ingo Molnar <mingo@elte.hu> wrote: > > > > * Yinghai Lu <yhlu.kernel@gmail.com> wrote: > > > >> > BIOS-e820: 0000000077ff0000 - 0000000078000000 (reserved) > >> > BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved) > >> > BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved) > >> > > >> > which overlaps with the chipset PCI BAR (hpet) resource: > >> > > >> > pci 0000:00:14.0: BAR has HPET at fed00000-fed003ff > >> > > >> > so due to this 1K conflict we take the full e820-reserved entry out and > >> > give the range 0xfec00000-0x100000000 as 'free'. > >> > >> 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? I > > thought it would only succeed if the new resource was smaller than (a > > subset of) the existing resource. In the other direction, when a newly > > inserted resource is a superset of the existing resource, i thought we'd > > fail. > > > > 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 > > > > i.e. we have: > > > > [... PCI BAR ...] > > [... e820 reservation ...] > > > > in that case the insert_resource() will fail due to the conflict. Can we > > declare it in that case that the e820 reserved entry is mortally broken > > and we just ignore it? > > yes, that will fail to insert ... > > expand to 0xfeb0f000 - 0xfffffff and try again.? > > may need to update insert_resource to return conflict resource ...
yes, that sounds an excellent idea - i was thinking of something muchmore complex like breaking up the reserved entry - but indeed just creating a large enough superset should be perfect. I.e. extend both start and end until we fit fully. [or reach some natural boundary such as 0 or 4GB]
> > At least we should emit a prominent warning if insert_resource() fails, > > and add in an mdelay(2000) so that the user sees it. > > right
btw., perhaps we should try this: first try a request_resource(). If that fails it means we overlap with something - then we should already printk a warning. (e820 reserved entries should never conflict with PCI resources, should they?)
then try an insert_resource(). If that too fails it means a partial overlap - printk another warning. Try the extension (within reasonable limits) and retry.
Does that sound worthwile?
Ingo
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