[RFC PATCH 12/12] docs: add RISC-V Worlds next-wid/next-widlist DT properties

[Yu-Chien Peter Lin <peter.lin@sifive.com>]

Add device tree bindings for RISC-V Worlds support in OpenSBI
domains. These properties enable per-domain world isolation.

Per-domain properties:
  * next-wid - Sets mlwid CSR (requires Smlwid extension)
  * next-widlist - Sets mwiddeleg CSR (requires Smwiddeleg extension)

ROOT domain properties (in /chosen/opensbi-config):
  * root-domain-next-wid - mlwid for ROOT domain
  * root-domain-next-widlist - mwiddeleg for ROOT domain

Signed-off-by: Yu-Chien Peter Lin <peter.lin@sifive.com>
---
 docs/domain_support.md | 13 +++++++++++++
 docs/opensbi_config.md | 13 +++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/docs/domain_support.md b/docs/domain_support.md
index e267a9f7..164d87e6 100644
--- a/docs/domain_support.md
+++ b/docs/domain_support.md
@@ -91,6 +91,8 @@ following manner:
   is the next arg1 for the ROOT domain
 * **next_mode** - Next booting stage mode in coldboot HART scratch space
   is the next mode for the ROOT domain
+* **next_wid** - Next booting stage World ID
+* **next_widlist** - Next booting stage World ID delegation bitmask
 * **system_reset_allowed** - The ROOT domain is allowed to reset the system
 * **system_suspend_allowed** - The ROOT domain is allowed to suspend the system
 
@@ -200,6 +202,17 @@ The DT properties of a domain instance DT node are as follows:
   is used as default value. If this DT property is not available and
   coldboot HART is assigned to the domain instance then **next booting
   stage mode of coldboot HART** is used as default value.
+* **next-wid** (Optional) - The 32 bit World ID for lower-privilege modes
+  (S/U-mode) for the domain instance. If present, OpenSBI writes this value
+  to **mlwid** on context switch into this domain (requires Smlwid extension).
+  If absent, OpenSBI uses the platform M-mode WID from the **riscv,pmwid** DT
+  property as fallback, in which case the value must be identical across all
+  HARTs assigned to the domain. In either case, the value written to **mlwid**
+  must be permitted by **pmlwidlist** on every HART assigned to the domain.
+* **next-widlist** (Optional) - The 64 bit World ID delegation bitmask for
+  the domain instance. If present, OpenSBI writes this value to **mwiddeleg**
+  on context switch into this domain (requires Smwiddeleg extension). If absent,
+  clears **mwiddeleg** to disable S-mode WID delegation.
 * **system-reset-allowed** (Optional) - A boolean flag representing
   whether the domain instance is allowed to do system reset.
 * **system-suspend-allowed** (Optional) - A boolean flag representing
diff --git a/docs/opensbi_config.md b/docs/opensbi_config.md
index 104d82c9..b7210dfc 100644
--- a/docs/opensbi_config.md
+++ b/docs/opensbi_config.md
@@ -29,6 +29,19 @@ The DT properties of a domain configuration DT node are as follows:
 * **system-suspend-test** (Optional) - When present, enable a system
   suspend test implementation which simply waits five seconds and issues a WFI.
 
+* **root-domain-next-wid** (Optional) - The 32 bit World ID for lower-privilege
+  modes (S/U-mode) for the ROOT domain. If present, OpenSBI writes this value
+  to **mlwid** when entering the ROOT domain (requires Smlwid extension). If not
+  set, OpenSBI uses the platform M-mode WID from the **riscv,pmwid** DT property
+  as fallback, in which case the value must be identical across all HARTs assigned
+  to the ROOT domain. In either case, the value written to **mlwid** must be
+  permitted by **pmlwidlist** on every HART assigned to the ROOT domain.
+
+* **root-domain-next-widlist** (Optional) - The 64 bit World ID delegation bitmask
+  for the ROOT domain. If present, OpenSBI writes this value to **mwiddeleg** when
+  entering the ROOT domain (requires Smwiddeleg extension). If not set, clears
+  **mwiddeleg** to disable S-mode WID delegation.
+
 The OpenSBI Configuration Node will be deleted at the end of cold boot
 (replace the node (subtree) with nop tags).
 
-- 
2.43.7


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