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[v3,11/13] Documentation: riscv: Add sv48 description to VM layout

Message ID 20211206104657.433304-12-alexandre.ghiti@canonical.com
State Accepted
Commit 9d19f2b5256ef6cdd4947b48fab4032d0060e916
Headers show
Series Introduce sv48 support without relocatable kernel | expand

Commit Message

Alexandre Ghiti Dec. 6, 2021, 10:46 a.m. UTC 
sv48 was just introduced, so add its virtual memory layout to the
documentation.

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

diff --git a/Documentation/riscv/vm-layout.rst b/Documentation/riscv/vm-layout.rst
index 1bd687b97104..5b36e45fef60 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:
+  ____________________________________________________________|___________________________________________________________
+                    |            |                  |         |
+   ffff8d7ffee00000 |  -114.5 TB | ffff8d7ffeffffff |    2 MB | fixmap
+   ffff8d7fff000000 |  -114.5 TB | ffff8d7fffffffff |   16 MB | PCI io
+   ffff8d8000000000 |  -114.5 TB | ffff8f7fffffffff |    2 TB | vmemmap
+   ffff8f8000000000 |  -112.5 TB | ffffaf7fffffffff |   32 TB | vmalloc/ioremap space
+   ffffaf8000000000 |  -80.5  TB | ffffef7fffffffff |   64 TB | direct mapping of all physical memory
+   ffffef8000000000 |  -16.5  TB | fffffffeffffffff | 16.5 TB | kasan
+  __________________|____________|__________________|_________|____________________________________________________________
+                                                              |
+                                                              | 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
+  __________________|____________|__________________|_________|____________________________________________________________