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

Suzuki K Poulose
2026-03-19T10:43:11Z

On 18/03/2026 15:53, Steven Price wrote:
> The RMM may not be tracking all the memory of the system at boot. Create
> 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.

This is a little bit vague. Should we explicitly mention :

"For now we set the tracking_region_size to 0 for RMI_RMM_CONFIG_SET()"

> + * TODO: Support other granule sizes

nit: s/granule/Tracking/

Suzuki

> + */
> +#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
> +
> 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)
> +{
> + 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);
> +
> + 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 */
> }