> On 13 Mar 2025, at 11:02, Orzel, Michal <michal.or...@amd.com> wrote: > > > > On 13/03/2025 11:32, Luca Fancellu wrote: >> >> >> Hi Michal, >> >>> On 13 Mar 2025, at 10:19, Orzel, Michal <michal.or...@amd.com> wrote: >>> >>> >>> >>> On 12/03/2025 14:52, Luca Fancellu wrote: >>>> >>>> >>>> Rename the setup_pagetables function to setup_mappings in >>>> order to be implemented also for MPU system that does not >>>> have page tables. >>> >>> mappings is better than pagetables, so: >>> Reviewed-by: Michal Orzel <michal.or...@amd.com> >>> >>> but I'd like to understand what will be implementation of setup_mappings for >>> MPU. I suppose regions setup such that the following call to early_fdt_map >>> can >>> succeed and doing this in setup_mm is already too late? >> >> So on the MPU side, mappings are well defined in HW by registers, so we >> don’t need to >> allocate pagetables, so setup_mappings in reality will only prepare our >> logical data structure >> that tracks the MPU region state (few regions are already written by the asm >> early code and >> needs to be tracked). >> >> early_fdt_map won’t use this logical view of the MPU (as it’s called early), >> it will use low level >> API to access the MPU registers, like the early asm code did, basically to >> map the DTB. >> >> Doing that, we ensure that the current code flow in start_xen can be reused >> as it. > Then the question is: can the MPU part be moved to setup_mm if early_fdt_map > does not need setup_mappings? If so, we can avoid introducing a function with > a > name that is at least odd in MPU context and leave setup_pagetables only for > MMU. Adding a function with not ideal name just for the sake of avoiding > #ifdef > MMU does not sound like a good idea for me. > > You can check with others on this one.
I think you are right, I could provide a stub implementation for setup_pagetables() on MPU since there are no pagetables and introduce earlier setup_mm which will setup the datastructure. I don’t think anyone will oppose to that, so if I don’t ear from anyone I will drop this patch and implement the above > > ~Michal >
