On Thu, Jan 13, 2022 at 07:33:11PM +0200, Mike Rapoport wrote: > 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. > > 2) Just deal with it at a lower (arm64) level? > > 3) Some other way? > > We've discussed this with Ard on IRC, and our conclusion was that on arm64 > kdump kernel should have memblock.memory exactly the same as the normal > kernel. Then, the memory outside usable-memory-range should be reserved so > that kdump kernel won't step over it. > > With that, simple (untested) patch below could be what we need: > > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c > index bdca35284ceb..371418dffaf1 100644 > --- a/drivers/of/fdt.c > +++ b/drivers/of/fdt.c > @@ -1275,7 +1275,8 @@ void __init early_init_dt_scan_nodes(void) > of_scan_flat_dt(early_init_dt_scan_memory, NULL); > > /* Handle linux,usable-memory-range property */ > - memblock_cap_memory_range(cap_mem_addr, cap_mem_size); > + memblock_reserve(0, cap_mem_addr); > + memblock_reserve(cap_mem_addr + cap_mem_size, PHYS_ADDR_MAX); > } > > bool __init early_init_dt_scan(void *params) Thanks for discussing this further! I tried the above change, although I wrapped it in an if (cap_mem_size != 0), so that a normal kernel doesn't get its entire memory marked as reserved. The crash kernel hung without producing output - I haven't chased that down. This particular kernel was a bit older (5.15), so I'll try again with 5.17-rc to make sure. - Frank
