x86/ucode: Only rescan features on successful microcode load

Commit Message

Andrew Cooper Nov. 19, 2024, 9:58 p.m. UTC

There's no point rescanning if we didn't load something new.  Take the
opportunity to make the comment a bit more concise.

Signed-off-by: Andrew Cooper <[e-mail]>
---
CC: Jan Beulich <[e-mail]>
CC: Roger Pau Monné <[e-mail]>
---
 xen/arch/x86/cpu/microcode/core.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

Patch

diff --git a/xen/arch/x86/cpu/microcode/core.c b/xen/arch/x86/cpu/microcode/core.c
index 4811b5ffb11c..2bf462bf0c2e 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -860,6 +860,10 @@  static int __init early_microcode_load(struct boot_info *bi)
 
     rc = ucode_ops.apply_microcode(patch, 0);
 
+    if ( rc == 0 )
+        /* Rescan CPUID/MSR features, which may have changed after a load. */
+        early_cpu_init(false);
+
  unmap:
     bootstrap_unmap();
 
@@ -911,14 +915,5 @@  int __init early_microcode_init(struct boot_info *bi)
 
     rc = early_microcode_load(bi);
 
-    /*
-     * Some CPUID leaves and MSRs are only present after microcode updates
-     * on some processors. We take the chance here to make sure what little
-     * state we have already probed is re-probed in order to ensure we do
-     * not use stale values. tsx_init() in particular needs to have up to
-     * date MSR_ARCH_CAPS.
-     */
-    early_cpu_init(false);
-
     return rc;
 }