Hi Wei,
On 22/02/18 16:35, Wei Liu wrote:
On Wed, Feb 21, 2018 at 02:02:51PM +0000, Julien Grall wrote:
The function populate_pt_range is used to populate in advance the
page-table but it will not do the actual mapping. So passing the MFN in
parameter is pointless. Note that the only caller pass 0...
At the same time replace 0 by INVALID_MFN to make clear the MFN is
invalid.
The mfn parameter is the first mfn of a consecutive nr MFNs passed to
map_pages_to_xen. Putting INVALID_MFN isn't helping -- the value written
to page table(s) will wrap around to 0.
And I think starting from 0 to avoid overflow is probably a better
behaviour. If you really want to make sure all entries are filled with
INVALID_MFN you should call map_pages_to_xen for nr times with each
page.
I am not sure to understand this. From its name, populate_pt_range
should only create the intermediate tables. The leaf entry will stay
invalid. So how the value of mfn matters? Is it because the code is
written in a such way that passing INVALID_MFN will result to undefined
behavior?
Cheers,
--
Julien Grall
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