Re: [PATCH] percpu: km: ensure it is used with NOMMU (either UP or SMP)
From: Dennis Zhou <dennis@kernel.org>
Date: 2021-11-30 17:41:39
Hello, On Tue, Nov 30, 2021 at 05:29:54PM +0000, Vladimir Murzin wrote:
quoted hunk ↗ jump to hunk
Currently, NOMMU pull km allocator via !SMP dependency because most of them are UP, yet for SMP+NOMMU vm allocator gets pulled which: * may lead to broken build [1] * ...or not working runtime due to [2] It looks like SMP+NOMMU case was overlooked in bbddff054587 ("percpu: use percpu allocator on UP too") so restore that. [1] For ARM SMP+NOMMU (R-class cores) arm-none-linux-gnueabihf-ld: mm/percpu.o: in function `pcpu_post_unmap_tlb_flush': mm/percpu-vm.c:188: undefined reference to `flush_tlb_kernel_range' [2] static inline int vmap_pages_range_noflush(unsigned long addr, unsigned long end, pgprot_t prot, struct page **pages, unsigned int page_shift) { return -EINVAL; } Signed-off-by: Vladimir Murzin <redacted> --- mm/Kconfig | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)diff --git a/mm/Kconfig b/mm/Kconfig index d16ba92..66331e0 100644 --- a/mm/Kconfig +++ b/mm/Kconfig@@ -425,9 +425,8 @@ config THP_SWAP # UP and nommu archs use km based percpu allocator # config NEED_PER_CPU_KM - depends on !SMP bool - default y + default !SMP || !MMU
Should this be `depends on !SMP || !MMU` with default yes? Because with SMP && MMU, it shouldn't be an option to run with percpu-km.
config CLEANCACHE bool "Enable cleancache driver to cache clean pages if tmem is present" -- 2.7.4
It's interesting to me that this is all coming up at once. Earlier this month I had the same conversation with people involved with sh [1]. [1] https://lore.kernel.org/linux-sh/YY7tp5attRyK42Zk@fedora/ (local) I can pull this shortly once I see whatever happened to linux-sh. Thanks, Dennis