Messages in this thread | | | Date | Mon, 17 Apr 2023 17:18:09 +0100 | Subject | Re: [PATCH v3 32/60] arm64: head: allocate more pages for the kernel mapping | From | Ryan Roberts <> |
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On 17/04/2023 17:11, Ard Biesheuvel wrote: > On Mon, 17 Apr 2023 at 17:48, Ryan Roberts <ryan.roberts@arm.com> wrote: >> >> On 07/03/2023 14:04, Ard Biesheuvel wrote: >>> In preparation for switching to an early kernel mapping routine that >>> maps each segment according to its precise boundaries, and with the >>> correct attributes, let's allocate some extra pages for page tables for >>> the 4k page size configuration. This is necessary because the start and >>> end of each segment may not be aligned to the block size, and so we'll >>> need an extra page table at each segment boundary. >>> >>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> >>> --- >>> arch/arm64/include/asm/kernel-pgtable.h | 11 ++++++++++- >>> 1 file changed, 10 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h >>> index 4d13c73171e1e360..50b5c145358a5d8e 100644 >>> --- a/arch/arm64/include/asm/kernel-pgtable.h >>> +++ b/arch/arm64/include/asm/kernel-pgtable.h >>> @@ -80,7 +80,7 @@ >>> + EARLY_PGDS((vstart), (vend), add) /* each PGDIR needs a next level page table */ \ >>> + EARLY_PUDS((vstart), (vend), add) /* each PUD needs a next level page table */ \ >>> + EARLY_PMDS((vstart), (vend), add)) /* each PMD needs a next level page table */ >>> -#define INIT_DIR_SIZE (PAGE_SIZE * EARLY_PAGES(KIMAGE_VADDR, _end, EARLY_KASLR)) >>> +#define INIT_DIR_SIZE (PAGE_SIZE * (EARLY_PAGES(KIMAGE_VADDR, _end, EARLY_KASLR) + EARLY_SEGMENT_EXTRA_PAGES)) >>> >>> /* the initial ID map may need two extra pages if it needs to be extended */ >>> #if VA_BITS < 48 >>> @@ -101,6 +101,15 @@ >>> #define SWAPPER_TABLE_SHIFT PMD_SHIFT >>> #endif >>> >>> +/* The number of segments in the kernel image (text, rodata, inittext, initdata, data+bss) */ >>> +#define KERNEL_SEGMENT_COUNT 5 >>> + >>> +#if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN >>> +#define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1) >> >> I'm guessing the block size for 4K pages is PMD, so you need these extra pages >> to define PTEs for the case where the section start/end addresses are not on >> exact 2MB boundaries? But in that case, isn't it possible that you would need 2 >> extra PTE tables per segment - one for the start and one for the end? >> > > The end of one segment is the start of another, so we need one at the > start, plus one each for each segment end.
Ahh, of course. Thanks.
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