Re: [Xen-devel] [PATCH 14/17] xen/arm64: head: Remove ID map as soon as it is not used

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 26 Jun 2019, Julien Grall wrote:
> Hi Stefano,
> 
> On 6/26/19 9:25 PM, Stefano Stabellini wrote:
> > On Mon, 10 Jun 2019, Julien Grall wrote:
> > > The ID map may clash with other parts of the Xen virtual memory layout.
> > > At the moment, Xen is handling the clash by only creating a mapping to
> > > the runtime virtual address before enabling the MMU.
> > > 
> > > The rest of the mappings (such as the fixmap) will be mapped after the
> > > MMU is enabled. However, the code doing the mapping is not safe as it
> > > replace mapping without using the Break-Before-Make sequence.
> > > 
> > > As the ID map can be anywhere in the memory, it is easier to remove all
> > > the entries added as soon as the ID map is not used rather than adding
> > > the Break-Before-Make sequence everywhere.
> > 
> > I think it is a good idea, but I would ask you to mention 1:1 map
> > instead of "ID map" in comments and commit messages because that is the
> > wording we used in all comments so far (see the one in
> > create_page_tables and mm.c). It is easier to grep and refer to if we
> > use the same nomenclature. Note that I don't care about which
> > nomenclature we decide to use, I am only asking for consistency.
> > Otherwise, it would also work if you say it both way at least once:
> > 
> >   The ID map (1:1 map) may clash [...]
> 
> I would rather drop the wording 1:1 as this is confusing. It is also not
> trivial to find anything on google typing "1:1".

That's fine too

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