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

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

On 29/09/2026 23:17, Shanker Donthineni wrote:
> Hi Suzuki,
> 
> On 9/24/2026 8:52 AM, Suzuki K Poulose wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> 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.

Like the commit description says here ...


>> +/*
>> + * Make sure the area is tracked by RMM at FINE granularity.
>> + * We do not support changing the tracking yet.
>> + */
>> +static int rmi_verify_memory_tracking(phys_addr_t start, phys_addr_t 
>> end)
>> +{
>> +       while (start < end) {
>> +               unsigned long ret, category, state, next;
>> +
>> +               ret = rmi_granule_tracking_get(start, end, &category, 
>> &state, &next);
>> +               if (ret != RMI_SUCCESS)
>> +                       return -ENOMEM;
>> +
>> +               if (WARN_ON(next <= start))
>> +                       return -ENXIO;
>> +
>> +               if (state != RMI_TRACKING_FINE ||
>> +                   category != RMI_MEM_CATEGORY_CONVENTIONAL) {
>> +                       /* TODO: Set granule tracking in this case */
>> +                       pr_err("Granule tracking for region isn't 
>> fine/conventional: %llx-%lx\n",
>> +                              start, next);
>> +                       return -ENODEV;
> 
> This rejects any region the RMM does not already report as FINE,
> but the initial tracking state is IMPLEMENTATION DEFINED, nothing
> in DEN0137 Beta3 requires it to be FINE out of reset, and the full
> RMI_TRACKING_* range is legal to observe here.

Agreed. This was a deliberate decision to keep this series simple.
Once we have a base support merged, we can add support for dynamic
tracking and GPTs.

Kind regards
Suzuki


> 
> On NVIDIA platforms it is not FINE, so this path fails and CCA cannot
> be enabled at all. The TODO above is therefore load-bearing rather than
> an optimisation: the driver has to promote the region with
> RMI_GRANULE_TRACKING_SET and re-query, not bail out.


> 
> -Shanker
> 
>> +               }
>> +               start = next;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +/*
>> + * rmi_gpt_info - Query the GPT info for the given PAR.
>> + * @start: Base of the physical address region
>> + * @end: Top of the physical address region
>> + * @out_top: Top of the physical address region for which
>> + *             the GPT @out_gpt_par_state is valid
>> + * @out_gpt_par_state: State of the GPT covered by [start, out_top)
>> + */
>> +static long rmi_gpt_info(unsigned long start, unsigned long end,
>> +                        unsigned long *out_top,
>> +                        unsigned long *out_gpt_par_state)
>> +{
>> +       struct arm_smccc_1_2_regs regs = {
>> +               SMC_RMI_GPT_INFO, start, end,
>> +       };
>> +
>> +       rmi_smccc_invoke(&regs);
>> +       if (regs.a0 != RMI_SUCCESS)
>> +               return regs.a0;
>> +
>> +       if (out_top)
>> +               *out_top = regs.a1;
>> +       if (out_gpt_par_state)
>> +               *out_gpt_par_state = regs.a2;
>> +
>> +       return RMI_SUCCESS;
>> +}
>> +
>> +/*
>> + * We do not support creating L1 GPTs yet. So, make sure that
>> + * all the regions are managed by the firmware.
>> + */
>> +static int rmi_verify_gpt_firmware_managed(phys_addr_t start, 
>> phys_addr_t end)
>> +{
>> +       unsigned long l0gpt_sz;
>> +       unsigned long next, par_state;
>> +
>> +       l0gpt_sz = 1UL << (30 + FIELD_GET(RMI_FEATURE_REGISTER_1_L0GPTSZ,
>> +                                         rmi_feat_reg(1)));
>> +       start = ALIGN_DOWN(start, l0gpt_sz);
>> +       end = ALIGN(end, l0gpt_sz);
>> +
>> +       while (start < end) {
>> +               long ret = rmi_gpt_info(start, end, &next, &par_state);
>> +
>> +               if (ret != RMI_SUCCESS)
>> +                       return -ENOMEM;
>> +
>> +               if (WARN_ON(next <= start))
>> +                       return -ENXIO;
>> +
>> +               if (par_state != RMI_GPT_PAR_PLAT) {
>> +                       pr_err("GPT for the region is not managed by 
>> firmware %llx-%lx\n",
>> +                               start, next);
>> +                       return -ENOMEM;
>> +               }
>> +               start = next;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +static int rmi_prepare_memory(phys_addr_t start, phys_addr_t end)
>> +{
>> +       int ret;
>> +
>> +       if (start >= end)
>> +               return -EINVAL;
>> +
>> +       ret = rmi_verify_memory_tracking(start, end);
>> +       if (ret)
>> +               return ret;
>> +
>> +       return rmi_verify_gpt_firmware_managed(start, end);
>> +}
>> +
>> +static int rmi_init_metadata(void)
>> +{
>> +       phys_addr_t start, end;
>> +       struct memblock_region *r;
>> +
>> +       for_each_mem_region(r) {
>> +               int ret;
>> +
>> +               /* Firmware-reserved NOMAP regions are not usable 
>> system RAM */
>> +               if (memblock_is_nomap(r))
>> +                       continue;
>> +
>> +               start = PAGE_ALIGN(r->base);
>> +               end = PAGE_ALIGN_DOWN(r->base + r->size);
>> +               /* Too small ? */
>> +               if (start >= end)
>> +                       continue;
>> +
>> +               ret = rmi_prepare_memory(start, end);
>> +               if (ret)
>> +                       return ret;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +static int rmi_memory_notifier(struct notifier_block *nb,
>> +                              unsigned long action, void *data)
>> +{
>> +       struct memory_notify *arg = data;
>> +       phys_addr_t start, end;
>> +       int ret;
>> +
>> +       if (action != MEM_GOING_ONLINE)
>> +               return NOTIFY_DONE;
>> +
>> +       start = PFN_PHYS(arg->start_pfn);
>> +       end = PFN_PHYS(arg->start_pfn + arg->nr_pages);
>> +       ret = rmi_prepare_memory(start, end);
>> +
>> +       return notifier_from_errno(ret);
>> +}
>> +
>> +static struct notifier_block rmi_memory_nb = {
>> +       .notifier_call = rmi_memory_notifier,
>> +};
>> +
>> +bool is_rmi_available(void)
>> +{
>> +       return arm64_rmi_is_available;
>> +}
>> +EXPORT_SYMBOL_GPL(is_rmi_available);
>> +
>> +static int rmi_init_memory(void)
>> +{
>> +       int ret;
>> +
>> +       ret = rmi_init_metadata();
>> +       if (ret)
>> +               return ret;
>> +
>> +       return register_memory_notifier(&rmi_memory_nb);
>> +}
>> +
>>   static int __init arm64_init_rmi(void)
>>   {
>>          int ret;
>> @@ -843,9 +1049,19 @@ static int __init arm64_init_rmi(void)
>>          if (ret) {
>>                  pr_err("RMM activate failed (%d)\n", ret);
>>                  ret = ret < 0 ? ret : -ENXIO;
>> +               return ret;
>>          }
>>
>> -       return ret;
>> +       ret = rmi_init_memory();
>> +       if (ret) {
>> +               /* Deactivate the RMM */
>> +               WARN_ON(rmi_sro_memxfer_cmd(sro, GFP_KERNEL, 
>> SMC_RMI_RMM_DEACTIVATE));
>> +               return ret;
>> +       }
>> +
>> +       arm64_rmi_is_available = true;
>> +       pr_info("RMI configured\n");
>> +       return 0;
>>   }
>>
>>   /*
>> diff --git a/include/linux/arm-rmi-cmds.h b/include/linux/arm-rmi-cmds.h
>> index b03974fd8168c..5b177bb176326 100644
>> --- a/include/linux/arm-rmi-cmds.h
>> +++ b/include/linux/arm-rmi-cmds.h
>> @@ -70,6 +70,8 @@ static inline int rmi_undelegate_page(phys_addr_t phys)
>>          return rmi_undelegate_range(phys, PAGE_SIZE);
>>   }
>>
>> +bool is_rmi_available(void);
>> +
>>   long rmi_sro_memxfer_execute(struct rmi_sro_state *sro, gfp_t gfp);
>>   void rmi_sro_free(struct rmi_sro_state *sro);
>>   long rmi_sro_execute(struct arm_smccc_1_2_regs *regs);
>> -- 
>> 2.43.0
>>
>