Messages in this thread | | | From | Atish Patra <> | Date | Fri, 19 Jun 2020 11:16:47 -0700 | Subject | Re: [PATCH 2/2] riscv: Use PUD/PGDIR entries for linear mapping when possible |
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On Thu, Jun 18, 2020 at 9:28 PM Alex Ghiti <alex@ghiti.fr> wrote: > > Hi Atish, > > Le 6/18/20 à 8:47 PM, Atish Patra a écrit : > > On Wed, Jun 3, 2020 at 8:38 AM Alexandre Ghiti <alex@ghiti.fr> wrote: > >> Improve best_map_size so that PUD or PGDIR entries are used for linear > >> mapping when possible as it allows better TLB utilization. > >> > >> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> > >> --- > >> arch/riscv/mm/init.c | 45 +++++++++++++++++++++++++++++++++----------- > >> 1 file changed, 34 insertions(+), 11 deletions(-) > >> > >> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > >> index 9a5c97e091c1..d275f9f834cf 100644 > >> --- a/arch/riscv/mm/init.c > >> +++ b/arch/riscv/mm/init.c > >> @@ -424,13 +424,29 @@ static void __init create_pgd_mapping(pgd_t *pgdp, > >> create_pgd_next_mapping(nextp, va, pa, sz, prot); > >> } > >> > >> -static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size) > >> +static bool is_map_size_ok(uintptr_t map_size, phys_addr_t base, > >> + uintptr_t base_virt, phys_addr_t size) > >> { > >> - /* Upgrade to PMD_SIZE mappings whenever possible */ > >> - if ((base & (PMD_SIZE - 1)) || (size & (PMD_SIZE - 1))) > >> - return PAGE_SIZE; > >> + return !((base & (map_size - 1)) || (base_virt & (map_size - 1)) || > >> + (size < map_size)); > >> +} > >> + > >> +static uintptr_t __init best_map_size(phys_addr_t base, uintptr_t base_virt, > >> + phys_addr_t size) > >> +{ > >> +#ifndef __PAGETABLE_PMD_FOLDED > >> + if (is_map_size_ok(PGDIR_SIZE, base, base_virt, size)) > >> + return PGDIR_SIZE; > >> + > >> + if (pgtable_l4_enabled) > >> + if (is_map_size_ok(PUD_SIZE, base, base_virt, size)) > >> + return PUD_SIZE; > >> +#endif > >> + > >> + if (is_map_size_ok(PMD_SIZE, base, base_virt, size)) > >> + return PMD_SIZE; > >> > >> - return PMD_SIZE; > >> + return PAGE_SIZE; > >> } > >> > >> /* > >> @@ -576,7 +592,7 @@ void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size) > >> asmlinkage void __init setup_vm(uintptr_t dtb_pa) > >> { > >> uintptr_t va, end_va; > >> - uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE); > >> + uintptr_t map_size; > >> > >> load_pa = (uintptr_t)(&_start); > >> load_sz = (uintptr_t)(&_end) - load_pa; > >> @@ -587,6 +603,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) > >> > >> kernel_virt_addr = KERNEL_VIRT_ADDR; > >> > >> + map_size = best_map_size(load_pa, PAGE_OFFSET, MAX_EARLY_MAPPING_SIZE); > >> va_pa_offset = PAGE_OFFSET - load_pa; > >> va_kernel_pa_offset = kernel_virt_addr - load_pa; > >> pfn_base = PFN_DOWN(load_pa); > >> @@ -700,6 +717,8 @@ static void __init setup_vm_final(void) > >> > >> /* Map all memory banks */ > >> for_each_memblock(memory, reg) { > >> + uintptr_t remaining_size; > >> + > >> start = reg->base; > >> end = start + reg->size; > >> > >> @@ -707,15 +726,19 @@ static void __init setup_vm_final(void) > >> break; > >> if (memblock_is_nomap(reg)) > >> continue; > >> - if (start <= __pa(PAGE_OFFSET) && > >> - __pa(PAGE_OFFSET) < end) > >> - start = __pa(PAGE_OFFSET); > >> > >> - map_size = best_map_size(start, end - start); > >> - for (pa = start; pa < end; pa += map_size) { > >> + pa = start; > >> + remaining_size = reg->size; > >> + > >> + while (remaining_size) { > >> va = (uintptr_t)__va(pa); > >> + map_size = best_map_size(pa, va, remaining_size); > >> + > >> create_pgd_mapping(swapper_pg_dir, va, pa, > >> map_size, PAGE_KERNEL); > >> + > >> + pa += map_size; > >> + remaining_size -= map_size; > >> } > >> } > >> > > This may not work in the RV32 with 2G memory and if the map_size is > > determined to be a page size > > for the last memblock. Both pa & remaining_size will overflow and the > > loop will try to map memory from zero again. > > I'm not sure I understand: if pa starts at 0x8000_0000 and size is 2G, > then pa will overflow in the last iteration, but remaining_size will > then be equal to 0 right ? > Not unless the remaining_size is at least page size aligned. The last remaining size would "fff". It will overflow as well after subtracting the map_size.
> And by the way, I realize that this loop only handles sizes that are > aligned on map_size. >
Yeah.
> Thanks, > > Alex > > > > > >> -- > >> 2.20.1 > >> > >> > >
-- Regards, Atish
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