[PATCHv3 02/11] arm64: Handle section maps for swapper/idmap
Suzuki K. Poulose
Suzuki.Poulose at arm.com
Wed Oct 14 06:21:24 PDT 2015
On 14/10/15 13:06, Mark Rutland wrote:
> On Wed, Oct 14, 2015 at 12:20:25PM +0100, Suzuki K. Poulose wrote:
>> We use section maps with 4K page size to create the swapper/idmaps.
>> So far we have used !64K or 4K checks to handle the case where we
>> use the section maps.
>> This patch adds a new symbol, ARM64_SWAPPER_USES_SECTION_MAPS, to
>> handle cases where we use section maps, instead of using the page size
>> Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> Cc: Mark Rutland <mark.rutland at arm.com>
>> Cc: Catalin Marinas <catalin.marinas at arm.com>
>> Cc: Will Deacon <will.deacon at arm.com>
>> Signed-off-by: Suzuki K. Poulose <suzuki.poulose at arm.com>
>> arch/arm64/include/asm/kernel-pgtable.h | 31 ++++++++-----
>> arch/arm64/mm/mmu.c | 72 ++++++++++++++-----------------
>> 2 files changed, 52 insertions(+), 51 deletions(-)
>> diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
>> index 622929d..5876a36 100644
>> --- a/arch/arm64/include/asm/kernel-pgtable.h
>> +++ b/arch/arm64/include/asm/kernel-pgtable.h
>> @@ -19,6 +19,13 @@
>> #ifndef __ASM_KERNEL_PGTABLE_H
>> #define __ASM_KERNEL_PGTABLE_H
>> +/* With 4K pages, we use section maps. */
>> +#ifdef CONFIG_ARM64_4K_PAGES
>> +#define ARM64_SWAPPER_USES_SECTION_MAPS 1
>> +#define ARM64_SWAPPER_USES_SECTION_MAPS 0
> The comment is somewhat redunant. It would be better to state why we do
> this for 4K and not 64K (or 16K).
Something like :
* ARM64 kernel is guaranteed to be loaded at 2M aligned
* address (as per booting requirements). Hence we can use
* section mapping with 4K (section size = 2M) and not with
* 16K(section size = 32M) or 64K (section size = 512M).
>> + * us PUD_SIZE (with SECTION maps, i.e, 4K) or PMD_SIZE (without
>> + * SECTION maps, i.e, 64K pages) memory starting from PHYS_OFFSET
>> + * (which must be aligned to 2MB as per Documentation/arm64/booting.txt).
> This didn't seem to get updated for 16K later in the series, unless I
> missed something.
> Perhaps drop the mention of 4K / 64K entirely here?
You are right, I missed it. We can drop the pagesize info entirely.
>> @@ -551,7 +552,7 @@ int kern_addr_valid(unsigned long addr)
>> return pfn_valid(pte_pfn(*pte));
>> #ifdef CONFIG_SPARSEMEM_VMEMMAP
>> -#ifdef CONFIG_ARM64_64K_PAGES
>> +#if !ARM64_SWAPPER_USES_SECTION_MAPS
> This leaves the comments on the #else and #endif stale. Please update
> those too.
More information about the linux-arm-kernel