[PATCH v2 13/13] kho: Add Kconfig option to enable KHO by default

[Pasha Tatashin]

Currently, Kexec Handover must be explicitly enabled via the kernel
command line parameter `kho=on`.

For workloads that rely on KHO as a foundational requirement (such as
the upcoming Live Update Orchestrator), requiring an explicit boot
parameter adds redundant configuration steps.

Introduce CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT. When selected, KHO
defaults to enabled. This is equivalent to passing kho=on at boot.
The behavior can still be disabled at runtime by passing kho=off.

Signed-off-by: Pasha Tatashin <pasha.tatashin at soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt at kernel.org>
---
 kernel/liveupdate/Kconfig          | 14 ++++++++++++++
 kernel/liveupdate/kexec_handover.c |  2 +-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig
index eae428309332..a973a54447de 100644
--- a/kernel/liveupdate/Kconfig
+++ b/kernel/liveupdate/Kconfig
@@ -37,4 +37,18 @@ config KEXEC_HANDOVER_DEBUGFS
 	  Also, enables inspecting the KHO fdt trees with the debugfs binary
 	  blobs.
 
+config KEXEC_HANDOVER_ENABLE_DEFAULT
+	bool "Enable kexec handover by default"
+	depends on KEXEC_HANDOVER
+	help
+	  Enable Kexec Handover by default. This avoids the need to
+	  explicitly pass 'kho=on' on the kernel command line.
+
+	  This is useful for systems where KHO is a prerequisite for other
+	  features, such as Live Update, ensuring the mechanism is always
+	  active.
+
+	  The default behavior can still be overridden at boot time by
+	  passing 'kho=off'.
+
 endmenu
diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index a7f876ece445..224bdf5becb6 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -52,7 +52,7 @@ union kho_page_info {
 
 static_assert(sizeof(union kho_page_info) == sizeof(((struct page *)0)->private));
 
-static bool kho_enable __ro_after_init;
+static bool kho_enable __ro_after_init = IS_ENABLED(CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT);
 
 bool kho_is_enabled(void)
 {
-- 
2.52.0.rc1.455.g30608eb744-goog