linux-kernel - Re: [PATCH v2 7/9] riscv: Align the sv39 linear map to 16 GiB

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Message-ID: <e8cf563f-d840-4e33-9ca0-2fa734c9f6c2@ghiti.fr>
Date: Tue, 5 Nov 2024 14:55:01 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Samuel Holland <samuel.holland@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, linux-riscv@...ts.infradead.org,
 Andrey Ryabinin <ryabinin.a.a@...il.com>,
 Alexander Potapenko <glider@...gle.com>,
 Andrey Konovalov <andreyknvl@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>,
 Vincenzo Frascino <vincenzo.frascino@....com>, kasan-dev@...glegroups.com
Cc: llvm@...ts.linux.dev, Catalin Marinas <catalin.marinas@....com>,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Alexandre Ghiti <alexghiti@...osinc.com>, Will Deacon <will@...nel.org>,
 Evgenii Stepanov <eugenis@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 7/9] riscv: Align the sv39 linear map to 16 GiB

On 22/10/2024 03:57, Samuel Holland wrote:
> The KASAN implementation on RISC-V requires the shadow memory for the
> vmemmap and linear map regions to be aligned to a PMD boundary (1 GiB).


PUD boundary


> For KASAN_GENERIC (KASAN_SHADOW_SCALE_SHIFT == 3), this enforces 8 GiB
> alignment for the memory regions themselves. KASAN_SW_TAGS uses 16-byte
> granules (KASAN_SHADOW_SCALE_SHIFT == 4), so now the memory regions must
> be aligned to a 16 GiB boundary.
>
> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
> ---
>
> (no changes since v1)
>
>   Documentation/arch/riscv/vm-layout.rst | 10 +++++-----
>   arch/riscv/include/asm/page.h          |  2 +-
>   2 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/arch/riscv/vm-layout.rst b/Documentation/arch/riscv/vm-layout.rst
> index eabec99b5852..c0778c421b34 100644
> --- a/Documentation/arch/riscv/vm-layout.rst
> +++ b/Documentation/arch/riscv/vm-layout.rst
> @@ -47,11 +47,11 @@ RISC-V Linux Kernel SV39
>                                                                 | Kernel-space virtual memory, shared between all processes:
>     ____________________________________________________________|___________________________________________________________
>                       |            |                  |         |
> -   ffffffc4fea00000 | -236    GB | ffffffc4feffffff |    6 MB | fixmap
> -   ffffffc4ff000000 | -236    GB | ffffffc4ffffffff |   16 MB | PCI io
> -   ffffffc500000000 | -236    GB | ffffffc5ffffffff |    4 GB | vmemmap
> -   ffffffc600000000 | -232    GB | ffffffd5ffffffff |   64 GB | vmalloc/ioremap space
> -   ffffffd600000000 | -168    GB | fffffff5ffffffff |  128 GB | direct mapping of all physical memory
> +   ffffffc2fea00000 | -244    GB | ffffffc2feffffff |    6 MB | fixmap
> +   ffffffc2ff000000 | -244    GB | ffffffc2ffffffff |   16 MB | PCI io
> +   ffffffc300000000 | -244    GB | ffffffc3ffffffff |    4 GB | vmemmap
> +   ffffffc400000000 | -240    GB | ffffffd3ffffffff |   64 GB | vmalloc/ioremap space
> +   ffffffd400000000 | -176    GB | fffffff3ffffffff |  128 GB | direct mapping of all physical memory
>                       |            |                  |         |
>      fffffff700000000 |  -36    GB | fffffffeffffffff |   32 GB | kasan
>     __________________|____________|__________________|_________|____________________________________________________________
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index 32d308a3355f..6e2f79cf77c5 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -37,7 +37,7 @@
>    * define the PAGE_OFFSET value for SV48 and SV39.
>    */
>   #define PAGE_OFFSET_L4		_AC(0xffffaf8000000000, UL)
> -#define PAGE_OFFSET_L3		_AC(0xffffffd600000000, UL)
> +#define PAGE_OFFSET_L3		_AC(0xffffffd400000000, UL)
>   #else
>   #define PAGE_OFFSET		_AC(CONFIG_PAGE_OFFSET, UL)
>   #endif /* CONFIG_64BIT */


Other than the nit above (that I think should be fixed though), you can add:

Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks,

Alex