x86/AMD-ucode: correct multiple container handling

Avoid emitting an error message referring to an incorrect or corrupt
container file just because no entry was found for the running CPU.

Additionally switch the order of data validation and consumption in
cpu_request_microcode()'s first loop, and also check the types of
skipped blocks in container_fast_forward().

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/microcode_amd.c
+++ b/xen/arch/x86/microcode_amd.c
@@ -331,12 +331,17 @@ static int container_fast_forward(const 
              header[1] == UCODE_EQUIV_CPU_TABLE_TYPE )
             break;
 
+        if ( header[0] != UCODE_UCODE_TYPE )
+            return -EINVAL;
         size = header[1] + SECTION_HDR_SIZE;
         if ( size < PATCH_HDR_SIZE || size_left < size )
             return -EINVAL;
 
         size_left -= size;
         *offset += size;
+
+        if ( !size_left )
+            return -ENODATA;
     }
 
     return 0;
@@ -386,10 +391,6 @@ static int cpu_request_microcode(int cpu
             break;
         }
 
-        if ( find_equiv_cpu_id(mc_amd->equiv_cpu_table, current_cpu_id,
-                               &equiv_cpu_id) )
-                break;
-
         /*
          * Could happen as we advance 'offset' early
          * in install_equiv_cpu_table
@@ -401,7 +402,16 @@ static int cpu_request_microcode(int cpu
             break;
         }
 
+        if ( find_equiv_cpu_id(mc_amd->equiv_cpu_table, current_cpu_id,
+                               &equiv_cpu_id) )
+            break;
+
         error = container_fast_forward(buf, bufsize - offset, &offset);
+        if ( error == -ENODATA )
+        {
+            ASSERT(offset == bufsize);
+            break;
+        }
         if ( error )
         {
             printk(KERN_ERR "microcode: CPU%d incorrect or corrupt container file\n"