On 14.11.25 08:30, Mike Rapoport wrote:
On Mon, Nov 10, 2025 at 01:07:15PM -0500, Pasha Tatashin wrote:
Upcoming LUO requires KHO for its operations, the requirement to place
both KHO=on and liveupdate=on becomes redundant. Set KHO to be enabled
by default.
I though more about this and it seems too much of a change. kho=1 enables
scratch areas and that significantly changes how free pages are distributed
in the free lists.
Let's go with a Kconfig option we discussed of-list:
(this is on top of the current mmotm/mm-nonmm-unstable)
From 823299d80aa4f7c16ef6cfd798a19e1dfe1a91ab Mon Sep 17 00:00:00 2001
From: Pasha Tatashin <[email protected]>
Date: Fri, 14 Nov 2025 09:27:47 +0200
Subject: [PATCH] kho: Allow KHO to be enabled by default
Upcoming LUO requires KHO for its operations, the requirement to place
both KHO=on and liveupdate=on becomes reduntant. Let's allow KHO to be
enabled by default, and CONFIG_LIVEUPDATE can select this CONFIG.
Looks much better, yes :). You can also imply this option automatically
when LUO=y.
Reviewed-by: Alexander Graf <[email protected]>
Alex
Signed-off-by: Pasha Tatashin <[email protected]>
Signed-off-by: Mike Rapoport (Microsoft) <[email protected]>
---
kernel/liveupdate/Kconfig | 8 ++++++++
kernel/liveupdate/kexec_handover.c | 2 +-
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig
index d7344d347f69..25c9a4d7781f 100644
--- a/kernel/liveupdate/Kconfig
+++ b/kernel/liveupdate/Kconfig
@@ -63,4 +63,12 @@ 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 the kexec handover by default. It is equivalent of passing
+ kho=on via kernel parameter, and can be overwritten to off via
+ kho=off.
+
endmenu
diff --git a/kernel/liveupdate/kexec_handover.c
b/kernel/liveupdate/kexec_handover.c
index 568cd9fe9aca..23a3df297bb3 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -51,7 +51,7 @@ union kho_page_info {
static_assert(sizeof(union kho_page_info) == sizeof(((struct page
*)0)->private));
-static bool kho_enable __ro_after_init = true;
+static bool kho_enable __ro_after_init =
IS_ENABLED(CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT);
bool kho_is_enabled(void)
{
--
2.50.1
--
Sincerely yours,
Mike.
Amazon Web Services Development Center Germany GmbH
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