Despite having kernel arguments to enable gigantic hugepages, this provides a way for the architecture to disable gigantic hugepages on the fly, similar to what we do for hugepages. Components like fadump (PowerPC-specific) need this functionality to disable gigantic hugepages when the kernel is booted solely to collect the kernel core dump. Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> Cc: Muchun Song <muchun.song@xxxxxxxxx> Cc: Madhavan Srinivasan <maddy@xxxxxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: linux-mm@xxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Signed-off-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx> --- To evaluate the impact of this change on architectures other than PowerPC, I did the following analysis: For architectures where hugepages_supported() is not redefined, it depends on HPAGE_SHIFT, which is found to be a constant. It is mostly initialized to PMD_SHIFT. Architecture : HPAGE_SHIFT initialized with ARC: PMD_SHIFT (constant) ARM: PMD_SHIFT (constant) ARM64: PMD_SHIFT (constant) Hexagon: 22 (constant) LoongArch: (PAGE_SHIFT + PAGE_SHIFT - 3) (appears to be constant) MIPS: (PAGE_SHIFT + PAGE_SHIFT - 3) (appears to be constant) PARISC: PMD_SHIFT (appears to be constant) RISC-V: PMD_SHIFT (constant) SH: 16 | 18 | 20 | 22 | 26 (constant) SPARC: 23 (constant) So seems like this change shouldn't have any impact on above architectures. On the S390 and X86 architectures, hugepages_supported() is redefined, and I am uncertain at what point it is safe to call hugepages_supported(). --- mm/hugetlb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index cec4b121193f..48b42b8d26b4 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4629,7 +4629,7 @@ static int __init hugepages_setup(char *s) * But we need to allocate gigantic hstates here early to still * use the bootmem allocator. */ - if (hugetlb_max_hstate && hstate_is_gigantic(parsed_hstate)) + if (hugetlb_max_hstate && hstate_is_gigantic(parsed_hstate) && hugepages_supported()) hugetlb_hstate_alloc_pages(parsed_hstate); last_mhp = mhp; -- 2.47.1
