Re: [PATCH v9 02/10] of: reserved_mem: Introduce "ll-map" property

[Thierry Reding]

On Thu, Sep 03, 2026 at 11:03:12AM +0100, Vincent Donnefort wrote:
> On Wed, Sep 02, 2026 at 12:24:36PM -0500, Rob Herring wrote:
> > On Wed, Sep 02, 2026 at 11:47:04AM +0100, Vincent Donnefort wrote:
> > > Keeping last-level mappings is interesting on some architectures as it
> > > allows mapping/unmapping pages from the kernel direct map without the
> > > risk of splitting blocks which, under the break-before-make rule, may
> > > trigger page-faults the kernel can't handle.
> > > 
> > > Add an "ll-map" property for reserved-memory regions. When set, it
> > > splits the underlying memblock and sets the MEMBLOCK_LLMAP flag.
> > 
> > Where is this documented? Any DT property must have a schema.
> 
> Ack.
> 
> > 
> > Though I'm not thrilled about more flag properties. Handling all the 
> > combinations of properties has proven to be painful. Can this be implied 
> > from the compatible string instead?
> > 
> > Rob
> 
> We need this before the kernel direct map has been created (paging_init()).
> 
> I would have moved that directly into the driver lend_pool.c, but then it is
> probed too late (unflatten_device_tree()).

Any of the node_*() callbacks from struct reserved_mem_ops get called
prior to paging_init(), so these could be used to manually set the
memblock flags in the corresponding drivers.

Thierry

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