Re: [PATCH v20 6/9] firmware: arm_rmm: Ensure the RMM has GPT entries for memory

[Catalin Marinas <catalin.marinas@arm.com>]

On Tue, Sep 29, 2026 at 11:16:20PM +0100, Suzuki K Poulose wrote:
> From: Steven Price <steven.price@arm.com>
> 
> The RMM maintains the state of all the granules in the system to make
> sure that the host is abiding by the rules. This state can be maintained
> at different granularity, per page (TRACKING_FINE) or per region
> (TRACKING_COARSE or TRACKING_INTERMEDIATE). The region size depends on the
> underlying "RMI_GRANULE_SIZE". For a "coarse"/"intermediate" region,
> all pages in the region must be of the same state, this implies we need to
> have "fine" tracking for DRAM, so that we can delegate individual pages.
> 
> For now we only support a statically carved out memory for tracking
> granules for the "fine" regions. This can be extended in the future to
> allow modifying the tracking granularity and remove the need for a
> static allocation by the firmware.
> 
> Similarly, the firmware may create L0 GPT entries describing the total
> address space. But if we change the "PAS" (Physical Address Space) of a
> granule, then the firmware may need to create L1 tables to track the PAS
> at a finer granularity. Linux therefore checks if the platform firmware
> manages the PAR region. i.e., the firmware is in charge of managing the
> L1 GPTs (creation and the required memory for the GPT tables - via static
> carveouts) without host intervention. Support for dynamic GPT creation by
> the host will be added later.
> 
> If the firmware requires us to manage the tracking or GPT memory,
> deactivate the RMM and reclaim any memory donated at RMM activation.
> 
> Apply the same checks when hotplugged memory is brought online.
> 
> Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Tested-by: Gavin Shan <gshan@redhat.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>