[PATCH 03/15] arm64: Introduce helpers for page table levels
Suzuki K. Poulose
Suzuki.Poulose at arm.com
Wed Oct 7 02:51:16 PDT 2015
On 07/10/15 09:26, Christoffer Dall wrote:
> Hi Suzuki,
> On Tue, Sep 15, 2015 at 04:41:12PM +0100, Suzuki K. Poulose wrote:
>> From: "Suzuki K. Poulose" <suzuki.poulose at arm.com>
>> Introduce helpers for finding the number of page table
>> levels required for a given VA width, shift for a particular
>> page table level.
>> Convert the existing users to the new helpers. More users
>> to follow.
>> 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>
>> Reviewed-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> Tested-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> arch/arm64/include/asm/pgtable-hwdef.h | 15 ++++++++++++---
>> 1 file changed, 12 insertions(+), 3 deletions(-)
>> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
>> index 24154b0..ce18389 100644
>> --- a/arch/arm64/include/asm/pgtable-hwdef.h
>> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
>> @@ -16,13 +16,21 @@
>> #ifndef __ASM_PGTABLE_HWDEF_H
>> #define __ASM_PGTABLE_HWDEF_H
>> + * Number of page-table levels required to address 'va_bits' wide
>> + * address, without section mapping
>> + */
>> +#define ARM64_HW_PGTABLE_LEVELS(va_bits) (((va_bits) - 4) / (PAGE_SHIFT - 3))
> I don't understand the '(va_bits) - 4' here, can you explain it (and add a
> comment to that effect) ?
As mentioned, I will change it to DIV_ROUND_UP() as suggested by Marc.
>> +#define ARM64_HW_PGTABLE_LEVEL_SHIFT(level) \
>> + ((PAGE_SHIFT - 3) * (level) + 3)
> While this change is clearly correct, if you can explain the math here
> in a comment as well, that would be helpful.
Sure, will add a comment to that effect.
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