Re: [Xen-devel] [xen-unstable test] 56456: regressions - FAIL

[Tim Deegan <tim@xxxxxxx>]

At 12:19 +0100 on 18 May (1431951570), Jan Beulich wrote:
> >>> On 18.05.15 at 12:50, <roger.pau@xxxxxxxxxx> wrote:
> > El 18/05/15 a les 12.17, Tim Deegan ha escrit:
> >>  - have map_dirty_bitmap() DTRT, with something like access_ok() +
> >>    a linear-pagetable lookup to find the frame.
> > 
> > That was my first intention, but AFAICT we have no function in tree to
> > resolve a PV guest VA into a GFN/MFN. The closest thing I could find was
> > using guest_walk_tables + guest_walk_to_gfn in order to obtain the gfn.
> > Should I send a patch to introduce a pv_gva_to_gfn function based on that?
> 
> Isn't that what we have the linear page table and guest_map_l1e()
> for?

Yes, or in this case guest_get_eff_l1e().  We'd want to make sure we
get_page() the underlying page as well to guard against it being freed
and reused while we have a mapping.

That won't check user/supervisor or write permissions in the upper
levels of the tree.  OTOH, __copy_to_user() doesn't either, so maybe
we don't care.  Jan, if you're happy with that then so am I.

Cheers,

Tim.

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