linux-kernel - [PATCH v2 08/10] Documentation: riscv: Add sv48 description to VM layout

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Date:   Wed, 29 Sep 2021 16:51:11 +0200
From:   Alexandre Ghiti <alexandre.ghiti@...onical.com>
To:     Jonathan Corbet <corbet@....net>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Zong Li <zong.li@...ive.com>, Anup Patel <anup@...infault.org>,
        Atish Patra <Atish.Patra@....com>,
        Christoph Hellwig <hch@....de>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Guo Ren <guoren@...ux.alibaba.com>,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
        Mayuresh Chitale <mchitale@...tanamicro.com>,
        linux-doc@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-efi@...r.kernel.org, linux-arch@...r.kernel.org
Cc:     Alexandre Ghiti <alexandre.ghiti@...onical.com>
Subject: [PATCH v2 08/10] Documentation: riscv: Add sv48 description to VM layout

sv48 was just introduced, so add its virtual memory layout to the
documentation.

Signed-off-by: Alexandre Ghiti <alexandre.ghiti@...onical.com>
---
 Documentation/riscv/vm-layout.rst | 36 +++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/Documentation/riscv/vm-layout.rst b/Documentation/riscv/vm-layout.rst
index b7f98930d38d..f10128e0a95f 100644
--- a/Documentation/riscv/vm-layout.rst
+++ b/Documentation/riscv/vm-layout.rst
@@ -61,3 +61,39 @@ RISC-V Linux Kernel SV39
    ffffffff00000000 |   -4    GB | ffffffff7fffffff |    2 GB | modules, BPF
    ffffffff80000000 |   -2    GB | ffffffffffffffff |    2 GB | kernel
   __________________|____________|__________________|_________|____________________________________________________________
+
+
+RISC-V Linux Kernel SV48
+------------------------
+
+::
+
+ ========================================================================================================================
+      Start addr    |   Offset   |     End addr     |  Size   | VM area description
+ ========================================================================================================================
+                    |            |                  |         |
+   0000000000000000 |    0       | 00007fffffffffff |  128 TB | user-space virtual memory, different per mm
+  __________________|____________|__________________|_________|___________________________________________________________
+                    |            |                  |         |
+   0000800000000000 | +128    TB | ffff7fffffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
+                    |            |                  |         | virtual memory addresses up to the -128 TB
+                    |            |                  |         | starting offset of kernel mappings.
+  __________________|____________|__________________|_________|___________________________________________________________
+                                                              |
+                                                              | Kernel-space virtual memory, shared between all processes:
+  ____________________________________________________________|___________________________________________________________
+                    |            |                  |         |
+   ffff800000000000 | -128    TB | ffff8fffffffffff |   16 TB | kasan
+   ffff9dfffee00000 |  -94    TB | ffff9dfffeffffff |    2 MB | fixmap
+   ffff9dffff000000 |  -94    TB | ffff9dffffffffff |   16 MB | PCI io
+   ffff9e0000000000 |  -94    TB | ffff9fffffffffff |    2 TB | vmemmap
+   ffffa00000000000 |  -92    TB | ffffbfffffffffff |   32 TB | vmalloc/ioremap space
+   ffffc00000000000 |  -64    TB | fffffffeffffffff |   64 TB | direct mapping of all physical memory
+  __________________|____________|__________________|_________|____________________________________________________________
+                                                              |
+                                                              | Identical layout to the 39-bit one from here on:
+  ____________________________________________________________|____________________________________________________________
+                    |            |                  |         |
+   ffffffff00000000 |   -4    GB | ffffffff7fffffff |    2 GB | modules, BPF
+   ffffffff80000000 |   -2    GB | ffffffffffffffff |    2 GB | kernel
+  __________________|____________|__________________|_________|____________________________________________________________
-- 
2.30.2