Re: [PATCHv2 1/3] arm64: Drop alloc function from create_mapping

From: Ard Biesheuvel
Date: Sat Jan 30 2016 - 05:35:47 EST


On 30 January 2016 at 00:46, Laura Abbott <labbott@xxxxxxxxxxxxxxxxx> wrote:
>
> create_mapping is only used in fixmap_remap_fdt. All the create_mapping
> calls need to happen on existing translation table pages without
> additional allocations. Rather than have an alloc function be called
> and fail, just set it to NULL and catch it's use. Also change

s/it's/its/

> the name to create_mapping_noalloc to better capture what exactly is
> going on.
>
> Signed-off-by: Laura Abbott <labbott@xxxxxxxxxxxxxxxxx>

With one nit below:
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

> ---
> arch/arm64/mm/mmu.c | 27 ++++++++++++++++++---------
> 1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 7711554..103ebc0 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -116,7 +116,9 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
> pte_t *pte;
>
> if (pmd_none(*pmd) || pmd_sect(*pmd)) {
> - phys_addr_t pte_phys = pgtable_alloc();
> + phys_addr_t pte_phys;
> + BUG_ON(!pgtable_alloc);
> + pte_phys = pgtable_alloc();
> pte = pte_set_fixmap(pte_phys);
> if (pmd_sect(*pmd))
> split_pmd(pmd, pte);
> @@ -158,7 +160,9 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
> * Check for initial section mappings in the pgd/pud and remove them.
> */
> if (pud_none(*pud) || pud_sect(*pud)) {
> - phys_addr_t pmd_phys = pgtable_alloc();
> + phys_addr_t pmd_phys;
> + BUG_ON(!pgtable_alloc);
> + pmd_phys = pgtable_alloc();
> pmd = pmd_set_fixmap(pmd_phys);
> if (pud_sect(*pud)) {
> /*
> @@ -223,7 +227,9 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
> unsigned long next;
>
> if (pgd_none(*pgd)) {
> - phys_addr_t pud_phys = pgtable_alloc();
> + phys_addr_t pud_phys;
> + BUG_ON(!pgtable_alloc);
> + pud_phys = pgtable_alloc();
> __pgd_populate(pgd, pud_phys, PUD_TYPE_TABLE);
> }
> BUG_ON(pgd_bad(*pgd));
> @@ -312,7 +318,10 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
> init_pgd(pgd_offset_raw(pgdir, virt), phys, virt, size, prot, alloc);
> }
>
> -static void __init create_mapping(phys_addr_t phys, unsigned long virt,
> +/*
> + * This function is for mapping using existing sections only.

Could you improve this comment? 'existing sections' does not quite
cover what we expect to deal with imo
> + */
> +static void __init create_mapping_noalloc(phys_addr_t phys, unsigned long virt,
> phys_addr_t size, pgprot_t prot)
> {
> if (virt < VMALLOC_START) {
> @@ -321,7 +330,7 @@ static void __init create_mapping(phys_addr_t phys, unsigned long virt,
> return;
> }
> __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
> - early_pgtable_alloc);
> + NULL);
> }
>
> void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
> @@ -680,7 +689,7 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
> /*
> * Make sure that the FDT region can be mapped without the need to
> * allocate additional translation table pages, so that it is safe
> - * to call create_mapping() this early.
> + * to call create_mapping_noalloc() this early.
> *
> * On 64k pages, the FDT will be mapped using PTEs, so we need to
> * be in the same PMD as the rest of the fixmap.
> @@ -696,8 +705,8 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
> dt_virt = (void *)dt_virt_base + offset;
>
> /* map the first chunk so we can read the size from the header */
> - create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
> - SWAPPER_BLOCK_SIZE, prot);
> + create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE),
> + dt_virt_base, SWAPPER_BLOCK_SIZE, prot);
>
> if (fdt_check_header(dt_virt) != 0)
> return NULL;
> @@ -707,7 +716,7 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
> return NULL;
>
> if (offset + size > SWAPPER_BLOCK_SIZE)
> - create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
> + create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
> round_up(offset + size, SWAPPER_BLOCK_SIZE), prot);
>
> memblock_reserve(dt_phys, size);
> --
> 2.5.0
>