On Fri Oct 10, 2025 at 5:38 PM IST, Ilias Apalodimas wrote: > Hi Anshul, > > On Fri, 10 Oct 2025 at 08:54, Anshul Dalal <[email protected]> wrote: >> >> For armv8, U-Boot uses a static map defined as 'mem_map' for configuring >> the MMU's page tables, done by mmu_setup. >> >> Though this works well for simpler platforms, it makes creating runtime >> carveouts by modifying the static array at runtime exceedingly complex >> like in mach-snapdragon/board.c. >> >> Creation of such carveouts is much better handled by APIs such as >> mmu_change_region_attr once the page tables are configured. Usually such >> carveouts are configured via the device-tree's reserved-memory node >> which provides the address and size for the carveout. >> >> Therefore this patch adds mmu_unmap_reserved_mem which acts as a wrapper >> over mmu_change_region_attr, helping unmap a reserved-memory region. >> >> Signed-off-by: Anshul Dalal <[email protected]> >> Tested-by: Wadim Egorov <[email protected]> >> --- >> arch/arm/cpu/armv8/cache_v8.c | 23 +++++++++++++++++++++++ >> arch/arm/include/asm/armv8/mmu.h | 9 +++++++++ >> 2 files changed, 32 insertions(+) >> >> diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c >> index cdf17d5f396..74814601483 100644 >> --- a/arch/arm/cpu/armv8/cache_v8.c >> +++ b/arch/arm/cpu/armv8/cache_v8.c >> @@ -86,6 +86,29 @@ int mem_map_fix_dram_banks(unsigned int index, unsigned >> int len, u64 attrs) >> >> return 0; >> } >> + >> +int mmu_unmap_reserved_mem(const char *name) >> +{ >> + void *fdt = (void *)gd->fdt_blob; >> + char node_path[128]; >> + fdt_addr_t addr; >> + fdt_size_t size; >> + int ret; >> + >> + snprintf(node_path, sizeof(node_path), "/reserved-memory/%s", name); >> + ret = fdt_path_offset(fdt, node_path); >> + if (ret < 0) >> + return ret; > > The DT spec defines a /reserved/ no-map; option for reserved memory > that should not participate in the memory map. > Is there any reason why we unconditionally unmap reserved memory and > not the no-map one only? >
I was expecting the caller to only try to unmap regions that already had no-map but we can add a check here too. Regards, Anshul
