Re: [PATCH v19 6/7] firmware: arm_rmm: Ensure the RMM has GPT entries for memory

[Gavin Shan <gshan@redhat.com>]

On 9/24/26 11:52 PM, 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.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> [ Switch to RMI_GPT_L1_INFO for checking GPTs and deactivate RMM ]
> Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
>   Changes since v19:
>       * Avoid mixing gotos with __free cleanups for arm64_init_rmi()
>   Changes since v18:
>       * Handle buggy RMM to make forward progress for RMI_GPT_INFO and
>         RMI_GRANULE_TRACKING_GET
>       * Make sure the memory ranges are not inverted and reject such ranges.
>       * Move granule_tracking_get/gpt_info wrappers closer to the callers
>         Drop "inline", let the compiler do its job
>   Changes since v17:
>       * Move wrappers that may not be used elsewhere, out of arm-rmi-cmds.h
>   Changes since v16:
>       * Check fine tracking and create L1 GPTs for hotplug-added memory.
>       * Clarify the L1 GPT setup and move the explanatory comment.
>       * Switch to using RMI_GPT_INFO command for checking the GPTs.
>       * Deactivate the RMM and reclaim the memory if we can't proceed.
>   Changes since v15:
>       * Skip firmware-reserved NOMAP memory in rmi_init_metadata()
>       * Handle negative error codes from wrappers.
>   Changes since v14:
>       * Move the implementation into drivers/firmware/arm_rmm.
>   Changes since v13:
>       * Moved out of KVM
> ---
>   drivers/firmware/arm_rmm/rmi.c | 218 ++++++++++++++++++++++++++++++++-
>   include/linux/arm-rmi-cmds.h   |   2 +
>   2 files changed, 219 insertions(+), 1 deletion(-)
> 

With Jonathan's comments addressed:

Reviewed-by: Gavin Shan <gshan@redhat.com>

Thanks,
Gavin