From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Wed, 6 Nov 2024 14:59:33 +0000 (+0000)
Subject: x86/ucode: Don't use microcode_update_cpu() in early_microcode_load()
X-Git-Tag: 4.20.0-rc1~186
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=41314ccee88839374f1a1a995bc7ae313f5ba272;p=xen.git

x86/ucode: Don't use microcode_update_cpu() in early_microcode_load()

There are two callers of microcode_update_cpu(), and because one passes NULL
and one doesn't, there are effectively two disjoint pieces of logic wrapped in
a single function.

early_microcode_load()'s use skips all the microcode_cache handling, and is
just a simple patch application.

Use ucode_ops.apply_microcode() directly, and remove the non-cache path from
microcode_update_cpu().  This skips a redundant collect_cpu_info()
call (performed in early_microcode_init(), marginally earlier), and avoids
holding microcode_mutex when we're not interacting with microcode_cache at
all.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---

diff --git a/xen/arch/x86/cpu/microcode/core.c b/xen/arch/x86/cpu/microcode/core.c
index 11cd878d1f..81a772cb2b 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -277,9 +277,7 @@ static int microcode_update_cpu(const struct microcode_patch *patch,
     alternative_vcall(ucode_ops.collect_cpu_info);
 
     spin_lock(&microcode_mutex);
-    if ( patch )
-        err = alternative_call(ucode_ops.apply_microcode, patch, flags);
-    else if ( microcode_cache )
+    if ( microcode_cache )
     {
         err = alternative_call(ucode_ops.apply_microcode, microcode_cache,
                                flags);
@@ -900,7 +898,7 @@ static int __init early_microcode_load(struct boot_info *bi)
      */
     early_mod_idx = idx;
 
-    rc = microcode_update_cpu(patch, 0);
+    rc = ucode_ops.apply_microcode(patch, 0);
 
  unmap:
     bootstrap_unmap();