On Wed, Nov 24, 2021 at 12:52 PM Guo Ren <guoren@xxxxxxxxxx> wrote: > > On Wed, Nov 24, 2021 at 2:55 PM Anup Patel <anup@xxxxxxxxxxxxxx> wrote: > > > > On Wed, Nov 24, 2021 at 11:35 AM <guoren@xxxxxxxxxx> wrote: > > > > > > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > > > > > > For small memory systems(Allwinner D1s/F133), one page size memory > > > cannot be ignored. > > > > > > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > > > Cc: Alexandre Ghiti <alex@xxxxxxxx> > > > Cc: Anup Patel <anup@xxxxxxxxxxxxxx> > > > Cc: Atish Patra <Atish.Patra@xxxxxxx> > > > > This PATCH breaks the CPU hotplug functionality. > > > > When a CPU/HART is turned off and turned on at runtime, the > > low-level relocate() will be called to enable MMU on the CPU > > being brought-up which in-turn uses trampoline_pg_dir. > Yeah, I forgot that. > > How about removing trampoline_pg_dir totally and using > early_pg_dir/swapper_pg_dir for relocate directly? The trampoline_pg_dir is to handle the case when RAM is large enough such that RAM physical address range overlaps kernel virtual address range (i.e. VA >= PAGE_OFFSET). This is overlap of virtual address range and physical address range can be problematic for low-level code which is trying to enable MMU (such as the relocate() function). Here's a old kernel thread which tries to summarize this: https://lore.kernel.org/lkml/CAAhSdy3URWHVY_GPNb2yRBuctRELRtTTWPM2OpwUVSRFAyXyiA@xxxxxxxxxxxxxx/ Regards, Anup > > > > > Regards, > > Anup > > > > > --- > > > arch/riscv/mm/init.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > > > index 24b2b8044602..097bb3bc4020 100644 > > > --- a/arch/riscv/mm/init.c > > > +++ b/arch/riscv/mm/init.c > > > @@ -241,9 +241,9 @@ unsigned long riscv_pfn_base __ro_after_init; > > > EXPORT_SYMBOL(riscv_pfn_base); > > > > > > pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss; > > > -pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss; > > > static pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss; > > > > > > +pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); > > > pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); > > > static pmd_t __maybe_unused early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE); > > > > > > -- > > > 2.25.1 > > > > > > > -- > Best Regards > Guo Ren > > ML: https://lore.kernel.org/linux-csky/
