Messages in this thread | | | From | Anup Patel <> | Date | Mon, 25 May 2020 11:42:05 +0530 | Subject | Re: [PATCH 6/8] riscv: Allow user to downgrade to sv39 when hw supports sv48 |
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On Sun, May 24, 2020 at 2:46 PM Alexandre Ghiti <alex@ghiti.fr> wrote: > > This is made possible by using the mmu-type property of the cpu node of > the device tree. > > By default, the kernel will boot with 4-level page table if the hw supports > it but it can be interesting for the user to select 3-level page table as > it is less memory consuming and faster since it requires less memory > accesses in case of a TLB miss. > > Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> > --- > arch/riscv/mm/init.c | 25 +++++++++++++++++++++++-- > 1 file changed, 23 insertions(+), 2 deletions(-) > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index bad8da099ff6..1776eeb53d61 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -509,11 +509,32 @@ void disable_pgtable_l4(void) > * then read SATP to see if the configuration was taken into account > * meaning sv48 is supported. > */ > -asmlinkage __init void set_satp_mode(uintptr_t load_pa) > +asmlinkage __init void set_satp_mode(uintptr_t load_pa, uintptr_t dtb_pa) > { > u64 identity_satp, hw_satp; > int cpus_node; > > + /* 1/ Check if the user asked for sv39 explicitly in the device tree */ > + cpus_node = fdt_path_offset((void *)dtb_pa, "/cpus"); > + if (cpus_node >= 0) { > + int node; > + > + fdt_for_each_subnode(node, (void *)dtb_pa, cpus_node) { > + const char *mmu_type = fdt_getprop((void *)dtb_pa, node, > + "mmu-type", NULL); > + if (!mmu_type) > + continue; > + > + if (!strcmp(mmu_type, "riscv,sv39")) { > + disable_pgtable_l4(); > + return; > + } > + > + break; > + } > + } > + > + /* 2/ Determine if the HW supports sv48: if not, fallback to sv39 */ > create_pgd_mapping(early_pg_dir, load_pa, (uintptr_t)early_pud, > PGDIR_SIZE, PAGE_TABLE); > create_pud_mapping(early_pud, load_pa, (uintptr_t)early_pmd, > @@ -561,7 +582,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) > load_sz = (uintptr_t)(&_end) - load_pa; > > #if defined(CONFIG_64BIT) && !defined(CONFIG_MAXPHYSMEM_2GB) > - set_satp_mode(load_pa); > + set_satp_mode(load_pa, dtb_pa); > #endif > > kernel_virt_addr = KERNEL_VIRT_ADDR; > -- > 2.20.1 >
Looks good to me.
Reviewed-by: Anup Patel <anup@brainfault.org>
Regards, Anup
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