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

[Suzuki K Poulose]

On 29/09/2026 23:29, 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@xxxxxxx>
> >
> > 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.

...

> > +
> > +/*
> > + * 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;
>
> Accepting only RMI_GPT_PAR_PLAT rules out the host ever creating its own
> L1 GPTs. On NVIDIA platforms the PARs backing system RAM come up as
> RMI_GPT_PAR_HOST_NOT_CREATED, so this returns -ENOMEM and CCA cannot be
> enabled at all.

Like I mentioned in the previous response, this is staged upstreaming.
The dynamic GPT/Tracking will follow after. This also calls for 
on-demand activation which Catalin requested and can be combined together,
as we dedicate quite a lot of memory for the metadata and L1GPTs.


> With local changes to promote granule tracking via RMI_GRANULE_TRACKING_SET
> and to create the host L1 GPTs, I was able to boot a Realm with multiple
> vCPUs and exercise basic boot functionality on NVIDIA silicon.

Thanks for the testing !

Cheers
Suzuki