Re: [Xen-devel] [PATCH] grant table and bogus mfns

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 13/11/07 16:40, "Kieran Mansley" <kmansley@xxxxxxxxxxxxxx> wrote:

> I'm slightly surprised that without the call to iomem_permit_access() I
> don't trip over the iomem_access_permitted() check in
> xen/arch/x86/mm.c:get_page_from_l1e() when the grant is mapped.  I hope
> this doesn't indicate that I've missed something.

get_page_from_l1e() is not executed on the map_grant path, which explains
this behaviour.

As for GNTMAP_nocache, I think actually we should not trust the mapper to
get the cache attributes correct (because sometimes if the attributes are
wrong the system can be destabilised). Actually we now in xen-unstable have
cache-attribute tracking for RAM pages. The cache attributes for the granted
mapping should pick up PAT/PWT/PCD from the page's count_info field. If dom0
has the page mapped with the right attributes this will then do the right
thing immediately. If dom0 doesn't have the page mapped then we'll need to
do a bit more work...

 -- Keir



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