Messages in this thread | | | Subject | Re: [PATCH 2/2] riscv: Use PUD/PGDIR entries for linear mapping when possible | From | Alex Ghiti <> | Date | Sun, 21 Jun 2020 05:39:51 -0400 |
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Hi Atish,
Le 6/20/20 à 5:04 AM, Alex Ghiti a écrit : > 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.
While fixing this issue, I noticed that if the size in the device tree is not aligned on PAGE_SIZE, the size is then automatically realigned on PAGE_SIZE: see early_init_dt_add_memory_arch where size is and-ed with PAGE_MASK to remove the unaligned part.
So the issue does not need to be fixed :)
Thanks anyway,
Alex
>> >>> 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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