[PATCH] x86/ucode: Add option to scan microcode by default

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

A lot of systems automatically add microcode to the initrd so it can be
useful as a vendor policy to always scan for microcode. Add a Kconfig
option to allow setting the default behaviour.

The default behaviour is unchanged since the new option defaults to
"no".

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
 xen/arch/x86/Kconfig              | 11 +++++++++++
 xen/arch/x86/cpu/microcode/core.c |  2 +-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 9cdd04721afa..b806d8bc3319 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -383,6 +383,17 @@ config ALTP2M
 
          If unsure, stay with defaults.
 
+config UCODE_SCAN_DEFAULT
+       def_bool n
+       prompt "Scan for microcode by default"
+       help
+         During boot, Xen can scan the multiboot images for a CPIO archive
+         containing CPU microcode to be loaded.
+
+         Enabling this option will cause Xen to scan for it by default.
+
+         If unsure, say N.
+
 endmenu
 
 source "common/Kconfig"
diff --git a/xen/arch/x86/cpu/microcode/core.c 
b/xen/arch/x86/cpu/microcode/core.c
index 87283cff1de4..de00c22b4bd6 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -100,7 +100,7 @@ static struct microcode_patch *microcode_cache;
  * location we require that they are not both active together.
  */
 static int __initdata opt_mod_idx;
-static bool __initdata opt_scan;
+static bool __initdata opt_scan = IS_ENABLED(CONFIG_UCODE_SCAN_DEFAULT);
 
 /*
  * Used by the EFI path only, when xen.cfg identifies an explicit microcode
-- 
2.48.1