Re: [PATCH v10 3/4] arm64: Implement page table free interfaces

Chintan Pandya
2018-05-24T14:59:42Z

On 5/24/2018 7:27 PM, Chintan Pandya wrote:
> Implement pud_free_pmd_page() and pmd_free_pte_page().
>
> Implementation requires,
> 1) Clearing off the current pud/pmd entry
> 2) Invalidate TLB which could have previously
> valid but not stale entry
> 3) Freeing of the un-used next level page tables
>
> Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>
> ---
> arch/arm64/mm/mmu.c | 34 ++++++++++++++++++++++++++++++----
> 1 file changed, 30 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index da98828..17d9282 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -45,6 +45,7 @@
> #include <asm/memblock.h>
> #include <asm/mmu_context.h>
> #include <asm/ptdump.h>
> +#include <asm/tlbflush.h>
>
> #define NO_BLOCK_MAPPINGS BIT(0)
> #define NO_CONT_MAPPINGS BIT(1)
> @@ -973,12 +974,37 @@ int pmd_clear_huge(pmd_t *pmdp)
> return 1;
> }
>
> -int pud_free_pmd_page(pud_t *pud, unsigned long addr)
> +int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
> {
> - return pud_none(*pud);
> + pmd_t *table;
> + pmd_t pmd;
> +
> + pmd = READ_ONCE(*pmdp);
> + if (pmd_present(pmd)) {
> + table = __va(pmd_val(pmd));
> + pmd_clear(pmdp);
> + __flush_tlb_kernel_pgtable(addr);
> + pte_free_kernel(NULL, (pte_t *) table);
> + }
> + return 1;
> }
>
> -int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
> +int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
> {
> - return pmd_none(*pmd);
> + pmd_t *table;
> + pud_t pud;
> + int i = 0;
> +
> + pud = READ_ONCE(*pudp);
> + if (pud_present(pud)) {
> + table = __va(pud_val(pud));
> + do {
> + pmd_free_pte_page(&table[i], addr + (i * PMD_SIZE));
> + } while (i++, i < PTRS_PER_PMD);
Hi Will,

Right after sending these patches, I realized that do-while condition
can be made to look like what we see in ioremap/vmalloc code. I guess,
that's what you suggested. So, I'll raise v11 fixing that. Any more
concerns ?

> +
> + pud_clear(pudp);
> + __flush_tlb_kernel_pgtable(addr);
> + pmd_free(NULL, table);
> + }
> + return 1;
> }
>

Chintan
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