linux-kernel - [RFC PATCH 5/7] riscv: Align the sv39 linear map to 16 GiB

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Message-ID: <20240814085618.968833-6-samuel.holland@sifive.com>
Date: Wed, 14 Aug 2024 01:55:33 -0700
From: Samuel Holland <samuel.holland@...ive.com>
To: 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,
	linux-kernel@...r.kernel.org,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Evgenii Stepanov <eugenis@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org,
	Samuel Holland <samuel.holland@...ive.com>
Subject: [RFC PATCH 5/7] riscv: Align the sv39 linear map to 16 GiB

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).
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>
---

 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 077b968dcc81..ed71b3b1b784 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 7ede2111c591..09d15567b0b8 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 */
-- 
2.45.1