[PATCH 2/2] microcode: Check whether the microcode is correct.

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

We do the microcode code update in two steps - the presmp:
 'microcode_presmp_init' and when CPUs are brought up:
'microcode_init'. The earlier performs the microcode update
on the BSP - but unfortunately it does not check whether the
update failed. Which means that we might try later to update
a incorrect payload on the rest of CPUs.

This patch handles this odd situation.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[v2: Redid it as we are not doing scan and <index> at the same time]
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/microcode.c |   17 ++++++++++++++++-
 1 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index e6344cf..091d5d1 100644
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -418,6 +418,7 @@ static int __init microcode_presmp_init(void)
         {
             void *data;
             size_t len;
+            int rc = 0;
 
             if ( ucode_blob.size )
             {
@@ -430,10 +431,24 @@ static int __init microcode_presmp_init(void)
                 data = ucode_mod_map(&ucode_mod);
             }
             if ( data )
-                microcode_update_cpu(data, len);
+                rc = microcode_update_cpu(data, len);
+            else
+                rc = -ENOMEM;
 
             if ( !ucode_blob.size )
                 ucode_mod_map(NULL);
+
+            if ( rc )
+            {
+                if ( ucode_blob.size )
+                {
+                    xfree(ucode_blob.data);
+                    ucode_blob.size = 0;
+                    ucode_blob.data = NULL;
+                }
+                else
+                    ucode_mod.mod_end = 0;
+            }
         }
 
         register_cpu_notifier(&microcode_percpu_nfb);
-- 
1.7.7.6