kho: warn if KHO is disabled due to an error

During boot scratch area is allocated based on command line parameters or
auto calculated.  However, scratch area may fail to allocate, and in that
case KHO is disabled.  Currently, no warning is printed that KHO is
disabled, which makes it confusing for the end user to figure out why KHO
is not available.  Add the missing warning message.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Pasha Tatashin <[email protected]>
Acked-by: Mike Rapoport (Microsoft) <[email protected]>
Acked-by: Pratyush Yadav <[email protected]>
Cc: Alexander Graf <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Changyuan Lyu <[email protected]>
Cc: Coiby Xu <[email protected]>
Cc: Dave Vasilevsky <[email protected]>
Cc: Eric Biggers <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: soleen

kernel/kexec_handover.c

@@ -564,6 +564,7 @@ static void __init kho_reserve_scratch(void)
 err_free_scratch_desc:
 	memblock_free(kho_scratch, kho_scratch_cnt * sizeof(*kho_scratch));
 err_disable_kho:
+	pr_warn("Failed to reserve scratch area, disabling kexec handover\n");
 	kho_enable = false;
 }