Re: [PATCH v13 10/48] arm64: RMI: Ensure that the RMM has GPT entries for memory

Steven Price
2026-03-19T15:20:22Z

On 19/03/2026 10:31, Suzuki K Poulose wrote:
> Hi Steven
>
> On 18/03/2026 15:53, Steven Price wrote:
>> The RMM may not be tracking all the memory of the system at boot. Create
>
> Looks good to me. Please find some suggestions below.
>
>
> May be add a bit more context here :
>
> 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 (COARSE),
> where the "region size" depends on the underlying "RMI_GRANULE_SIZE".
> The state of the "tracked area" must be the same. This implies, we may
> need to have "FINE" tracking for DRAM, so that we can start delegating
> PAGEs. For now, we only support RMM with statically carved out memory
> for tracking FINE granularity for the tracking regions. We will extend
> the support for modifying the TRACKING region in the future.
>
> Similarly, the firmware may create L0 GPT entries describing the total
> address space (think of this as Block mappings in the page tables). But
> if we change the "PAS" of a granule in the block mapping, we may need
> to create L1 tables to track the PAS at the finer granularity. For now
> we only support a system where the L1 GPTs are created at boot time
> and dynamic GPT support will be added later.

Thanks for the wording - that does indeed make things clearer. SRO
support will effectively enable the "future" items.

>> the necessary tracking state and GPTs within the RMM so that all boot
>> memory can be delegated to the RMM as needed during runtime.
>>
>> Note: support is currently missing for SROs which means that if the RMM
>> needs memory donating this will fail (and render CCA unusable in Linux).
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>> New patch for v13
>> ---
>>   arch/arm64/kvm/rmi.c | 89 ++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 89 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
>> index 9590dff9a2c1..80aedc85e94a 100644
>> --- a/arch/arm64/kvm/rmi.c
>> +++ b/arch/arm64/kvm/rmi.c
>> @@ -4,6 +4,7 @@
>>    */
>>     #include <linux/kvm_host.h>
>> +#include <linux/memblock.h>
>>     #include <asm/kvm_pgtable.h>
>>   #include <asm/rmi_cmds.h>
>> @@ -56,6 +57,18 @@ static int rmi_check_version(void)
>>       return 0;
>>   }
>>   +/*
>> + * These are the 'default' sizes when passing 0 as the
>> tracking_region_size.
>> + * TODO: Support other granule sizes
>> + */
>> +#ifdef CONFIG_PAGE_SIZE_4KB
>> +#define RMM_GRANULE_TRACKING_SIZE    SZ_1G
>> +#elif defined(CONFIG_PAGE_SIZE_16KB)
>> +#define RMM_GRANULE_TRACKING_SIZE    SZ_32M
>> +#elif defined(CONFIG_PAGE_SIZE_64KB)
>> +#define RMM_GRANULE_TRACKING_SIZE    SZ_512M
>> +#endif
>> +
>
> Probably this should be made a Kconfig option, like the VA_BITS we have
> today for each page size.

Yes that's probably a good option - note that for 4k page size there is
only the one option in the spec. So this is only relevant for 16K/64K.

Thanks for the other comment suggestions below (and in the other email)
- all good points.

Thanks,
Steve

>>   static int rmi_configure(void)
>>   {
>>       struct rmm_config *config __free(free_page) = NULL;
>> @@ -95,6 +108,80 @@ static int rmi_configure(void)
>>       return 0;
>>   }
>>   +static int rmi_verify_memory_tracking(phys_addr_t start,
>> phys_addr_t end)
>
> Could we add a comment what we are trying to do here ?
>
> /*
>  * Make sure the area is tracked by RMM at FINE granularity.
>  * We do not support changing the TRACKING yet. This will
>  * be added in the future.
>  */
>
>
>> +{
>> +    start = ALIGN_DOWN(start, RMM_GRANULE_TRACKING_SIZE);
>> +    end = ALIGN(end, RMM_GRANULE_TRACKING_SIZE);
>> +
>> +    while (start < end) {
>> +        unsigned long ret, category, state;
>> +
>> +        ret = rmi_granule_tracking_get(start, &category, &state);
>> +        if (ret != RMI_SUCCESS ||
>> +            state != RMI_TRACKING_FINE ||
>> +            category != RMI_MEM_CATEGORY_CONVENTIONAL) {
>> +            /* TODO: Set granule tracking in this case */
>> +            kvm_err("Granule tracking for region isn't fine/
>> conventional: %llx",
>> +                start);
>> +            return -ENODEV;
>> +        }
>> +        start += RMM_GRANULE_TRACKING_SIZE;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static unsigned long rmi_l0gpt_size(void)
>> +{
>> +    return 1UL << (30 + FIELD_GET(RMI_FEATURE_REGISTER_1_L0GPTSZ,
>> +                      rmm_feat_reg1));
>> +}
>> +
>> +static int rmi_create_gpts(phys_addr_t start, phys_addr_t end)
>> +{
>> +    unsigned long l0gpt_sz = rmi_l0gpt_size();
>> +
>> +    start = ALIGN_DOWN(start, l0gpt_sz);
>> +    end = ALIGN(end, l0gpt_sz);
>> +
>> +    while (start < end) {
>> +        int ret = rmi_gpt_l1_create(start);
>
> How about adding a comment here explaining why we look for RMI_ERROR_GPT ?
>
>
>>
>         /*
>          * Make sure the L1 GPT tables are created for the region.
>          * RMI_ERROR_GPT indicates the L1 table exists.
>          */
>  +
>> +        if (ret && ret != RMI_ERROR_GPT) {
>
>
>> +            /*
>> +             * FIXME: Handle SRO so that memory can be donated for
>> +             * the tables.
>> +             */
>> +            kvm_err("GPT Level1 table missing for %llx\n", start);
>> +            return -ENOMEM;
>> +        }
>> +        start += l0gpt_sz;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static int rmi_init_metadata(void)
>> +{
>> +    phys_addr_t start, end;
>> +    const struct memblock_region *r;
>> +
>> +    for_each_mem_region(r) {
>> +        int ret;
>> +
>> +        start = memblock_region_memory_base_pfn(r) << PAGE_SHIFT;
>> +        end = memblock_region_memory_end_pfn(r) << PAGE_SHIFT;
>> +        ret = rmi_verify_memory_tracking(start, end);
>> +        if (ret)
>> +            return ret;
>> +        ret = rmi_create_gpts(start, end);
>> +        if (ret)
>> +            return ret;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>   static int rmm_check_features(void)
>>   {
>>       if (kvm_lpa2_is_enabled() && !
>> rmi_has_feature(RMI_FEATURE_REGISTER_0_LPA2)) {
>> @@ -120,6 +207,8 @@ void kvm_init_rmi(void)
>>           return;
>>       if (rmi_configure())
>>           return;
>> +    if (rmi_init_metadata())
>> +        return;
>>         /* Future patch will enable static branch kvm_rmi_is_available */
>>   }
>