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Message-ID: <5614EB14.9040107@arm.com> Date: Wed, 7 Oct 2015 10:51:16 +0100 From: "Suzuki K. Poulose" <Suzuki.Poulose@....com> To: Christoffer Dall <christoffer.dall@...aro.org> Cc: linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org, ard.biesheuvel@...aro.org, Marc.Zyngier@....com, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu Subject: Re: [PATCH 03/15] arm64: Introduce helpers for page table levels 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@....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@...aro.org> >> Cc: Mark Rutland <mark.rutland@....com> >> Cc: Catalin Marinas <catalin.marinas@....com> >> Cc: Will Deacon <will.deacon@....com> >> Signed-off-by: Suzuki K. Poulose <suzuki.poulose@....com> >> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@...aro.org> >> Tested-by: Ard Biesheuvel <ard.biesheuvel@...aro.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. Suzuki -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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