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Message-ID: <20140501100612.GA2848@lvm> Date: Thu, 1 May 2014 03:06:12 -0700 From: Christoffer Dall <christoffer.dall@...aro.org> To: Jungseok Lee <jays.lee@...sung.com> Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu, Catalin.Marinas@....com, Marc Zyngier <Marc.Zyngier@....com>, linux-kernel@...r.kernel.org, linux-samsung-soc <linux-samsung-soc@...r.kernel.org>, steve.capper@...aro.org, sungjinn.chung@...sung.com, Arnd Bergmann <arnd@...db.de>, kgene.kim@...sung.com, ilho215.lee@...sung.com Subject: Re: [PATCH v5 3/6] arm64: Add a description on 48-bit address space with 4KB pages On Thu, May 01, 2014 at 11:34:05AM +0900, Jungseok Lee wrote: > This patch adds memory layout and translation lookup information > about 48-bit address space with 4K pages. The description is based > on 4 levels of translation tables. > > Cc: Catalin Marinas <catalin.marinas@....com> > Cc: Steve Capper <steve.capper@...aro.org> > Signed-off-by: Jungseok Lee <jays.lee@...sung.com> > Reviewed-by: Sungjinn Chung <sungjinn.chung@...sung.com> > --- > Documentation/arm64/memory.txt | 59 ++++++++++++++++++++++++++++++++++------ > 1 file changed, 51 insertions(+), 8 deletions(-) > > diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt > index d50fa61..8142709 100644 > --- a/Documentation/arm64/memory.txt > +++ b/Documentation/arm64/memory.txt > @@ -8,10 +8,11 @@ This document describes the virtual memory layout used by the AArch64 > Linux kernel. The architecture allows up to 4 levels of translation > tables with a 4KB page size and up to 3 levels with a 64KB page size. > > -AArch64 Linux uses 3 levels of translation tables with the 4KB page > -configuration, allowing 39-bit (512GB) virtual addresses for both user > -and kernel. With 64KB pages, only 2 levels of translation tables are > -used but the memory layout is the same. > +AArch64 Linux uses 3 levels and 4 levels of translation tables with uses either 3 or 4 levels of translation? > +the 4KB page configuration, allowing 39-bit (512GB) and 48-bit (256TB) > +virtual addresses, respectively, for both user and kernel. With 64KB > +pages, only 2 levels of translation tables are used but the memory layout > +is the same. Perhaps it's worth clarifying that with 64KB and 2 levels of translation tables we are limited to a 42-bit address space here. > > User addresses have bits 63:39 set to 0 while the kernel addresses have > the same bits set to 1. TTBRx selection is given by bit 63 of the > @@ -21,7 +22,7 @@ The swapper_pgd_dir address is written to TTBR1 and never written to > TTBR0. > > > -AArch64 Linux memory layout with 4KB pages: > +AArch64 Linux memory layout with 4KB pages + 3 levels: > > Start End Size Use > ----------------------------------------------------------------------- > @@ -48,7 +49,34 @@ ffffffbffc000000 ffffffbfffffffff 64MB modules > ffffffc000000000 ffffffffffffffff 256GB kernel logical memory map > > > -AArch64 Linux memory layout with 64KB pages: > +AArch64 Linux memory layout with 4KB pages + 4 levels: > + > +Start End Size Use > +----------------------------------------------------------------------- > +0000000000000000 0000ffffffffffff 256TB user > + > +ffff000000000000 ffff7bfffffeffff ~124TB vmalloc > + > +ffff7bffffff0000 ffff7bffffffffff 64KB [guard page] > + > +ffff7c0000000000 ffff7dffffffffff 2TB vmemmap > + > +ffff7e0000000000 ffff7ffffbbfffff ~2TB [guard, future vmmemap] hmm, I may be completely confused, but if VMALLOC_END is defined to be (PAGE_OFFSET - UL(0x400000000) - SZ_64K), how can we squeeze ~4TB into a 16 GB hole? > + > +ffff7ffffa000000 ffff7ffffaffffff 16MB PCI I/O space > + > +ffff7ffffb000000 ffff7ffffbbfffff 12MB [guard] > + > +ffff7ffffbc00000 ffff7ffffbdfffff 2MB earlyprintk device shouldn't this be "fixed mappings" now? > + > +ffff7ffffbe00000 ffff7ffffbffffff 2MB [guard] > + > +ffff7ffffc000000 ffff7fffffffffff 64MB modules > + > +ffff800000000000 ffffffffffffffff 128TB kernel logical memory map > + > + > +AArch64 Linux memory layout with 64KB pages + 2 levels: > > Start End Size Use > ----------------------------------------------------------------------- > @@ -75,7 +103,7 @@ fffffdfffc000000 fffffdffffffffff 64MB modules > fffffe0000000000 ffffffffffffffff 2TB kernel logical memory map > > > -Translation table lookup with 4KB pages: > +Translation table lookup with 4KB pages + 3 levels: > > +--------+--------+--------+--------+--------+--------+--------+--------+ > |63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0| > @@ -90,7 +118,22 @@ Translation table lookup with 4KB pages: > +-------------------------------------------------> [63] TTBR0/1 > > > -Translation table lookup with 64KB pages: > +Translation table lookup with 4KB pages + 4 levels: > + > ++--------+--------+--------+--------+--------+--------+--------+--------+ > +|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0| > ++--------+--------+--------+--------+--------+--------+--------+--------+ > + | | | | | | > + | | | | | v > + | | | | | [11:0] in-page offset > + | | | | +-> [20:12] L3 index > + | | | +-----------> [29:21] L2 index > + | | +---------------------> [38:30] L1 index > + | +-------------------------------> [47:39] L0 index > + +-------------------------------------------------> [63] TTBR0/1 > + > + > +Translation table lookup with 64KB pages + 2 levels: > > +--------+--------+--------+--------+--------+--------+--------+--------+ > |63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0| > -- > 1.7.10.4 > > -- 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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