[PATCH] x86/S3: restore MCE (APs) and add MTRR (BSP) init

[Jan Beulich <jbeulich@xxxxxxxx>]

MCE init for APs was broken when CPU feature re-checking was added. MTRR
(re)init for the BSP looks to never have been there on the resume path.

Fixes: bb502a8ca592 ("x86: check feature flags after resume")
Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Sadly we need to go by CPU number (zero vs non-zero) here. See the call
site of recheck_cpu_features() in enter_state().

--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -642,16 +642,21 @@ void identify_cpu(struct cpuinfo_x86 *c)
                               smp_processor_id());
        }
 
-       if (system_state == SYS_STATE_resume)
-               return;
+       if (system_state == SYS_STATE_resume) {
+               unsigned int cpu = smp_processor_id();
 
+               if (cpu)
+                       mcheck_init(&cpu_data[cpu], false);
+               else /* Yes, the BSP needs to use the AP function here. */
+                       mtrr_ap_init();
+       }
        /*
         * On SMP, boot_cpu_data holds the common feature set between
         * all CPUs; so make sure that we indicate which features are
         * common between the CPUs.  The first time this routine gets
         * executed, c == &boot_cpu_data.
         */
-       if ( c != &boot_cpu_data ) {
+       else if (c != &boot_cpu_data) {
                /* AND the already accumulated flags with these */
                for ( i = 0 ; i < NCAPINTS ; i++ )
                        boot_cpu_data.x86_capability[i] &= c->x86_capability[i];