On Tue, Jan 11, 2022 at 08:44:41PM +0000, Frank van der Linden wrote: > On Tue, Jan 11, 2022 at 12:31:58PM +0200, Mike Rapoport wrote: > > > --- a/include/linux/memblock.h > > > +++ b/include/linux/memblock.h > > > @@ -481,6 +481,8 @@ phys_addr_t memblock_reserved_size(void); > > > phys_addr_t memblock_start_of_DRAM(void); > > > phys_addr_t memblock_end_of_DRAM(void); > > > void memblock_enforce_memory_limit(phys_addr_t memory_limit); > > > +void memblock_set_usable_range(phys_addr_t base, phys_addr_t size); > > > +void memblock_enforce_usable_range(void); > > > void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size); > > > void memblock_mem_limit_remove_map(phys_addr_t limit); > > > > We already have 3 very similar interfaces that deal with memory capping. > > Now you suggest to add fourth that will "generically" solve a single use > > case of DT, EFI and kdump interaction on arm64. > > > > Looks like a workaround for a fundamental issue of incompatibility between > > DT and EFI wrt memory registration. > > Yep, I figured this would be the main argument against this - arm64 > already added several other more-or-less special cased interfaces over > time. > > I'm more than happy to solve this in a different way. > > What would you suggest: > > 1) Try to merge the similar interfaces in to one. This could be a nice cleanup regardless of how we handle "linux,usable-memory-range". > 2) Just deal with it at a lower (arm64) level? Probably it will be the simplest solution in the short term. > 3) Some other way? I'm not expert enough on DT and EFI to see how they communicate the linux,usable-memory-range property. One thought I have is since we already create a DT for kexec/kdump why can't we add some data to EFI memory description similar to linux,usable-memore-range? Another thing is, if we could presume that DT and EFI are consistent in their view what is the span of the physical memory, we could drop memblock_remove(EVERYTHIING) and early_init_dt_add_memory_arch() from efi_init::reserve_regions() and then the loop over EFI memory descriptors will only take care of reserved and nomap regions. > Thanks, > > - Frank > -- Sincerely yours, Mike.
