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From:   Zhaoyang Huang <huangzhaoyang@gmail.com>
Date:   Thu, 18 Nov 2021 19:39:43 +0800
Message-ID: <CAGWkznG-M985L6Zg89iv3171PWKscZ2cNwdL0F6A_bqs2zs7Dw@mail.gmail.com>
Subject: Re: [RFC PATCH] arch: arm64: try to use PTE_CONT when change page attr
To:     Ard Biesheuvel <ardb@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Mike Rapoport <rppt@kernel.org>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Jonathan Marek <jonathan@marek.ca>,
        Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

forget the criteria for judging the linear address range, so please
ignore this patch

On Thu, Nov 18, 2021 at 4:18 PM Huangzhaoyang <huangzhaoyang@gmail.com> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
>
> kernel will use the min granularity when rodata_full enabled which
> make TLB pressure high. Furthermore, there is no PTE_CONT applied.
> Try to improve these a little by apply PTE_CONT when change page's
> attr.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> ---
>  arch/arm64/mm/pageattr.c | 62 ++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 58 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index a3bacd7..0b6a354 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -61,8 +61,13 @@ static int change_memory_common(unsigned long addr, int numpages,
>         unsigned long start = addr;
>         unsigned long size = PAGE_SIZE * numpages;
>         unsigned long end = start + size;
> +       unsigned long cont_pte_start = 0;
> +       unsigned long cont_pte_end = 0;
> +       unsigned long cont_pmd_start = 0;
> +       unsigned long cont_pmd_end = 0;
> +       pgprot_t orig_set_mask = set_mask;
>         struct vm_struct *area;
> -       int i;
> +       int i = 0;
>
>         if (!PAGE_ALIGNED(addr)) {
>                 start &= PAGE_MASK;
> @@ -98,9 +103,58 @@ static int change_memory_common(unsigned long addr, int numpages,
>          */
>         if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
>                             pgprot_val(clear_mask) == PTE_RDONLY)) {
> -               for (i = 0; i < area->nr_pages; i++) {
> -                       __change_memory_common((u64)page_address(area->pages[i]),
> -                                              PAGE_SIZE, set_mask, clear_mask);
> +               cont_pmd_start = (start + ~CONT_PMD_MASK + 1) & CONT_PMD_MASK;
> +               cont_pmd_end = cont_pmd_start + ~CONT_PMD_MASK + 1;
> +               cont_pte_start = (start + ~CONT_PTE_MASK + 1) & CONT_PTE_MASK;
> +               cont_pte_end = cont_pte_start + ~CONT_PTE_MASK + 1;
> +
> +               if (addr <= cont_pmd_start && end > cont_pmd_end) {
> +                       do {
> +                               __change_memory_common((u64)page_address(area->pages[i]),
> +                                               PAGE_SIZE, set_mask, clear_mask);
> +                               i++;
> +                               addr++;
> +                       } while(addr < cont_pmd_start);
> +                       do {
> +                               set_mask = __pgprot(pgprot_val(set_mask) | PTE_CONT);
> +                               __change_memory_common((u64)page_address(area->pages[i]),
> +                                               PAGE_SIZE, set_mask, clear_mask);
> +                               i++;
> +                               addr++;
> +                       } while(addr < cont_pmd_end);
> +                       set_mask = orig_set_mask;
> +                       do {
> +                               __change_memory_common((u64)page_address(area->pages[i]),
> +                                               PAGE_SIZE, set_mask, clear_mask);
> +                               i++;
> +                               addr++;
> +                       } while(addr <= end);
> +               } else if (addr <= cont_pte_start && end > cont_pte_end) {
> +                       do {
> +                               __change_memory_common((u64)page_address(area->pages[i]),
> +                                               PAGE_SIZE, set_mask, clear_mask);
> +                               i++;
> +                               addr++;
> +                       } while(addr < cont_pte_start);
> +                       do {
> +                               set_mask = __pgprot(pgprot_val(set_mask) | PTE_CONT);
> +                               __change_memory_common((u64)page_address(area->pages[i]),
> +                                               PAGE_SIZE, set_mask, clear_mask);
> +                               i++;
> +                               addr++;
> +                       } while(addr < cont_pte_end);
> +                       set_mask = orig_set_mask;
> +                       do {
> +                               __change_memory_common((u64)page_address(area->pages[i]),
> +                                               PAGE_SIZE, set_mask, clear_mask);
> +                               i++;
> +                               addr++;
> +                       } while(addr <= end);
> +               } else {
> +                       for (i = 0; i < area->nr_pages; i++) {
> +                               __change_memory_common((u64)page_address(area->pages[i]),
> +                                               PAGE_SIZE, set_mask, clear_mask);
> +                       }
>                 }
>         }
>
> --
> 1.9.1
>