| Date | Mon, 17 Apr 2023 16:48:02 +0100 | Subject | Re: [PATCH v3 32/60] arm64: head: allocate more pages for the kernel mapping | From | Ryan Roberts <> |
| |
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?
> +#else > +#define EARLY_SEGMENT_EXTRA_PAGES 0 > +#endif > + > /* > * Initial memory map attributes. > */
|