[PATCH 3/3] rust: arch/um: Add support for CONFIG_RUST under x86_64 UML

[David Gow <davidgow@google.com>]

CONFIG_RUST currently supports x86_64, but does not support it under
UML. With the previous patches applied, adding support is trivial:
add CONFIG_HAVE_RUST to UML if X86_64 is set.

The scripts/generate_rust_target.rs file already checks for
CONFIG_X86_64, not CONFIG_X86, so is prepared for UML support.

The Rust support does not currently support X86_32.

Also, update the Rust architecture support documentation to not that
this is being maintained: I intend to look after this as best I can.

Signed-off-by: David Gow <davidgow@google.com>
---
 Documentation/rust/arch-support.rst | 2 ++
 arch/um/Kconfig                     | 1 +
 2 files changed, 3 insertions(+)

diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
index 6982b63775da..a526ca1c688b 100644
--- a/Documentation/rust/arch-support.rst
+++ b/Documentation/rust/arch-support.rst
@@ -17,3 +17,5 @@ Architecture  Level of support  Constraints
 ============  ================  ==============================================
 ``x86``       Maintained        ``x86_64`` only.
 ============  ================  ==============================================
+``um``        Maintained        ``x86_64`` only.
+============  ================  ==============================================
diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index ad4ff3b0e91e..4db186f019ae 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -28,6 +28,7 @@ config UML
 	select TRACE_IRQFLAGS_SUPPORT
 	select TTY # Needed for line.c
 	select HAVE_ARCH_VMAP_STACK
+	select HAVE_RUST			if X86_64
 
 config MMU
 	bool
-- 
2.39.0.314.g84b9a713c41-goog