x86/S3: Restore cr4 later during resume

Just like the BSP/AP paths, %cr4 is loaded with only PAE.  Defer restoring all
of %cr4 (MCE in particular) until all the system structures (IDT/TSS in
particular) have been loaded.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/acpi/suspend.c

@@ -43,6 +43,9 @@ void restore_rest_processor_state(void)
 {
     load_system_tables();
 
+    /* Restore full CR4 (inc MCE) now that the IDT is in place. */
+    write_cr4(mmu_cr4_features);
+
     /* Recover syscall MSRs */
     wrmsrl(MSR_LSTAR, saved_lstar);
     wrmsrl(MSR_CSTAR, saved_cstar);

xen/arch/x86/acpi/wakeup_prot.S

@@ -45,10 +45,6 @@ ENTRY(do_suspend_lowlevel)
 ENTRY(s3_resume)
         lgdt    boot_gdtr(%rip)
 
-        /* mmu_cr4_features contains latest cr4 setting */
-        mov     REF(mmu_cr4_features), GREG(ax)
-        mov     GREG(ax), %cr4
-
         mov     REF(saved_cr0), GREG(ax)
         mov     GREG(ax), %cr0