[PATCH] kernel config: don't automatically enable kexec handover (KHO)

[Dominik Csapak <d.csapak@proxmox.com>]

CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT is enabled by default in the
upstream ubuntu kernel config, but has a (probably) unintended
side-effect: when KHO is automatically enabled, the kernel reserves
scratch memory for the kernel handoff and marks it with MIGRATE_CMA to
prevent non-movable allocations there.

This causes unusual stats in /proc/meminfo, for example:

CmaTotal:              0 kB
CmaFree:         4894720 kB

which looks nonsensical on the surface. It also reduces the available
memory for e.g. guests with PCI passthrough, as pinner memory can't live
in these areas.

Since we don't use kexec handover by default, and it can still be
enabled on the kernel commandline (kho=on), disable it by default to
increase the available pinnable memory for guests.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 debian/rules.d/config-common.opts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/debian/rules.d/config-common.opts b/debian/rules.d/config-common.opts
index 64505b4..204bab4 100644
--- a/debian/rules.d/config-common.opts
+++ b/debian/rules.d/config-common.opts
@@ -68,3 +68,4 @@
 -d CONFIG_N_GSM
 -d UBSAN_BOUNDS
 -e CONFIG_RUST
+-d CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT
-- 
2.47.3