Messages in this thread | | | Subject | Re: [PATCH 2/2] riscv: Use PUD/PGDIR entries for linear mapping when possible | From | Alex Ghiti <> | Date | Sat, 20 Jun 2020 05:04:00 -0400 |
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Hi Atish,
Le 6/19/20 à 2:16 PM, Atish Patra a écrit : > 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 for noticing, I send a v2.
Alex
> >> Thanks, >> >> Alex >> >> >>>> -- >>>> 2.20.1 >>>> >>>> > >
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