diff mbox series

[v8,2/4] x86/microcode: Ignore microcode loading interface for revision = -1

Message ID 20230830155326.10199-3-alejandro.vallejo@cloud.com (mailing list archive)
State New, archived
Headers show
Series Prevent attempting updates known to fail | expand

Commit Message

Alejandro Vallejo Aug. 30, 2023, 3:53 p.m. UTC 
Some hypervisors report ~0 as the microcode revision to mean "don't issue
microcode updates". Ignore the microcode loading interface in that case.

Signed-off-by: Alejandro Vallejo <alejandro.vallejo@cloud.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
v8:
  * Added missing newline in printk statement
  * Reduced indentation of second line of printk statement
  * Turned printk statement to INFO (because that's now the default)
---
 xen/arch/x86/cpu/microcode/core.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/xen/arch/x86/cpu/microcode/core.c b/xen/arch/x86/cpu/microcode/core.c
index e5e03cad34..01f1dd4710 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -867,10 +867,23 @@  int __init early_microcode_init(unsigned long *module_map,
         return -ENODEV;
     }
 
-    microcode_grab_module(module_map, mbi);
-
     ucode_ops.collect_cpu_info();
 
+    /*
+     * Some hypervisors deliberately report a microcode revision of -1 to
+     * mean that they will not accept microcode updates. We take the hint
+     * and ignore the microcode interface in that case.
+     */
+    if ( this_cpu(cpu_sig).rev == ~0 )
+    {
+        printk(XENLOG_INFO "Microcode loading disabled due to: %s\n",
+               "rev = ~0");
+        ucode_ops.apply_microcode = NULL;
+        return -ENODEV;
+    }
+
+    microcode_grab_module(module_map, mbi);
+
     if ( ucode_mod.mod_end || ucode_blob.size )
         rc = early_microcode_update_cpu();