[xen master] x86/microcode: Allow reading microcode revision even if it can't be updated

[patchbot@xxxxxxx]

commit a00f12055d266a034eb05962810cba4f6b9b0300
Author:     Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
AuthorDate: Thu Jul 6 09:05:37 2023 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jul 6 09:05:37 2023 +0200

    x86/microcode: Allow reading microcode revision even if it can't be updated
    
    microcode_update_one() currently assumes all microcode handlers are set or
    none are. That won't be the case in a future patch, as apply_microcode()
    may not be set while the others are. Hence, this patch allows reading the
    microcode revision even if updating it is unavailable.
    
    Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/cpu/microcode/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/cpu/microcode/core.c 
b/xen/arch/x86/cpu/microcode/core.c
index c3fee62906..bec8b55db2 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -750,11 +750,12 @@ __initcall(microcode_init);
 /* Load a cached update to current cpu */
 int microcode_update_one(void)
 {
+    if ( ucode_ops.collect_cpu_info )
+        alternative_vcall(ucode_ops.collect_cpu_info);
+
     if ( !ucode_ops.apply_microcode )
         return -EOPNOTSUPP;
 
-    alternative_vcall(ucode_ops.collect_cpu_info);
-
     return microcode_update_cpu(NULL);
 }
 
--
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