Re: [PATCH 4/6] firmware: arm_rmm: Configure the RMM with the host's page size

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 15/07/2026 15:27, Steven Price wrote:
> RMM v2.0 brings the ability to set the RMM's granule size. Check the
> feature registers and configure the RMM so that it matches the host's
> page size. This means that operations can be done with a granularity
> equal to PAGE_SIZE.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> Changes since v14:
>   * Move the implementation into drivers/firmware/arm_rmm.
> Changes since v13:
>   * Moved out of KVM.
> ---
>   drivers/firmware/arm_rmm/rmi.c | 43 ++++++++++++++++++++++++++++++++++
>   1 file changed, 43 insertions(+)
> 
> diff --git a/drivers/firmware/arm_rmm/rmi.c b/drivers/firmware/arm_rmm/rmi.c
> index c4850976544f..e7ab4a7df3ca 100644
> --- a/drivers/firmware/arm_rmm/rmi.c
> +++ b/drivers/firmware/arm_rmm/rmi.c
> @@ -76,6 +76,45 @@ static int rmi_read_features(void)
>   	return 0;
>   }
>   
> +static int rmi_configure(void)
> +{
> +	unsigned long ret;
> +	struct rmm_config *config __free(free_page) = (struct rmm_config *)get_zeroed_page(GFP_KERNEL);
> +
> +	if (!config)
> +		return -ENOMEM;
> +
> +	switch (PAGE_SIZE) {
> +	case SZ_4K:
> +		config->rmi_granule_size = RMI_GRANULE_SIZE_4KB;
> +		break;
> +	case SZ_16K:
> +		config->rmi_granule_size = RMI_GRANULE_SIZE_16KB;
> +		break;
> +	case SZ_64K:
> +		config->rmi_granule_size = RMI_GRANULE_SIZE_64KB;
> +		break;
> +	default:
> +		BUILD_BUG();
> +	}
> +
> +	/*
> +	 * For now we set the tracking_region_size to 0 which is the only option
> +	 * for 4KB PAGE_SIZE (1GB for 4KB PAGE_SIZE, 32MB/512MB for 16KB/64KB).
> +	 * TODO: Support other tracking sizes via Kconfig option for other
> +	 * PAGE_SIZES
> +	 */
> +	config->tracking_region_size = 0;
> +
> +	ret = rmi_rmm_config_set(virt_to_phys(config));
> +	if (ret) {
> +		pr_err("RMM config set failed\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
>   static int __init arm64_init_rmi(void)
>   {
>   	int ret;
> @@ -89,6 +128,10 @@ static int __init arm64_init_rmi(void)
>   	if (ret)
>   		return ret;
>   
> +	ret = rmi_configure();
> +	if (ret)
> +		return ret;
> +

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>


>   	return 0;
>   }
>