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Re: port-xen/52016: Mismatch between mem_clusters and pmap_enter bounds check
On Wed, Mar 01, 2017 at 12:05:00PM +0000, coypu%SDF.ORG@localhost wrote:
> The following reply was made to PR port-xen/52016; it has been noted by GNATS.
> From: coypu%SDF.ORG@localhost
> To: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
> Cc: gnats-bugs%NetBSD.org@localhost
> Subject: Re: port-xen/52016: Mismatch between mem_clusters and pmap_enter
> bounds check
> Date: Wed, 1 Mar 2017 12:03:10 +0000
> From a really far from sufficiently thorough look at linux, it looks
> like it might be equivalent to putting stuff that is directly accessed
> within [pmap_pa_start,pmap_pa_end) and having magic to map it to
But then you may have holes in between pmap_pa_start and pmap_pa_end.
I think we should keep pmap_pa* for pseudo-physical addresses only,
and add something else for machine addresses - if we have a way to
know mappable machine addresses.
One problem is that you may want to map machine addresses which falls into
the pseudo-physical address range via /dev/mem. In this case you don't have
a way to know which kind of address this is.
Using /dev/mem for both kind of addresses is bogus.
> And we can decide for domU that some stuff points to a dummy page and
> so HYPERVISOR_mmu_update doesn't fail for it.
a domU doesn't need to map machine addresses via /dev/mem (and the hypervisor
won't allow it).
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
NetBSD: 26 ans d'experience feront toujours la difference
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