docs/zh_CN: add riscv vm-layout translation

Translate .../riscv/vm-layout.rst into Chinese.
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/b59965f7f88ea22ec824dc2e92561b018fd370d1.1646108017.git.siyanteng@loongson.cnSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/translations/zh_CN/riscv/index.rst

@@ -18,6 +18,7 @@ RISC-V 体系结构
     :maxdepth: 1
 
     boot-image-header
+    vm-layout
     pmu
     patch-acceptance
 

Documentation/translations/zh_CN/riscv/vm-layout.rst

+.. SPDX-License-Identifier: GPL-2.0
+.. include:: ../disclaimer-zh_CN.rst
+
+:Original: Documentation/riscv/vm-layout.rst
+
+:翻译:
+
+ 司延腾 Yanteng Si <siyanteng@loongson.cn>
+
+============================
+RISC-V Linux上的虚拟内存布局
+============================
+
+:作者: Alexandre Ghiti <alex@ghiti.fr>
+:日期: 12 February 2021
+
+这份文件描述了RISC-V Linux内核使用的虚拟内存布局。
+
+32位 RISC-V Linux 内核
+======================
+
+RISC-V Linux Kernel SV32
+------------------------
+
+TODO
+
+64位 RISC-V Linux 内核
+======================
+
+RISC-V特权架构文档指出，64位地址 "必须使第63-48位值都等于第47位，否则将发生缺页异常。"：这将虚
+拟地址空间分成两半，中间有一个非常大的洞，下半部分是用户空间所在的地方，上半部分是RISC-V Linux
+内核所在的地方。
+
+RISC-V Linux Kernel SV39
+------------------------
+
+::
+
+  ========================================================================================================================
+      开始地址       |   偏移      |     结束地址      |  大小    | 虚拟内存区域描述
+  ========================================================================================================================
+                    |            |                  |         |
+   0000000000000000 |    0       | 0000003fffffffff |  256 GB | 用户空间虚拟内存，每个内存管理器不同
+  __________________|____________|__________________|_________|___________________________________________________________
+                    |            |                  |         |
+   0000004000000000 | +256    GB | ffffffbfffffffff | ~16M TB | ... 巨大的、几乎64位宽的直到内核映射的-256GB地方
+                    |            |                  |         |     开始偏移的非经典虚拟内存地址空洞。
+                    |            |                  |         |
+  __________________|____________|__________________|_________|___________________________________________________________
+                                                              |
+                                                              | 内核空间的虚拟内存，在所有进程之间共享:
+  ____________________________________________________________|___________________________________________________________
+                    |            |                  |         |
+   ffffffc6fee00000 | -228    GB | ffffffc6feffffff |    2 MB | fixmap
+   ffffffc6ff000000 | -228    GB | ffffffc6ffffffff |   16 MB | PCI io
+   ffffffc700000000 | -228    GB | ffffffc7ffffffff |    4 GB | vmemmap
+   ffffffc800000000 | -224    GB | ffffffd7ffffffff |   64 GB | vmalloc/ioremap space
+   ffffffd800000000 | -160    GB | fffffff6ffffffff |  124 GB | 直接映射所有物理内存
+   fffffff700000000 |  -36    GB | fffffffeffffffff |   32 GB | kasan
+  __________________|____________|__________________|_________|____________________________________________________________
+                                                              |
+                                                              |
+  ____________________________________________________________|____________________________________________________________
+                    |            |                  |         |
+   ffffffff00000000 |   -4    GB | ffffffff7fffffff |    2 GB | modules, BPF
+   ffffffff80000000 |   -2    GB | ffffffffffffffff |    2 GB | kernel
+  __________________|____________|__________________|_________|____________________________________________________________