Re: [Xen-devel] [PATCH] xen/x86: Remap text/data/bss with appropriate permissions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.03.16 at 15:44, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 17/03/16 14:31, Jan Beulich wrote:
>> Also - do we really want to make this code dependent on
>> map_pages_to_xen() not intermediately zapping the mappings
>> being changed?
> 
> Do you mean "immediately"?

No.

> As far as I can tell, it is guaranteed to be safe, even when remapping
> the code section.  Updates to the live pagetables are using atomic
> writes, and I didn't spot a point which would end up with a transient
> non-present mapping.

But we may, at some point and for whatever reason, come to make
the function zap the mapping (i.e. clear the present bit), flush, and
only the re-establish the new mapping.

Jan


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