x86/speculation: Move arch_smt_update() call to after mitigation decisions

arch_smt_update() now has a dependency on both Spectre v2 and MDS
mitigations.  Move its initial call to after all the mitigation decisions
have been made.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>

CVE-2018-12126
CVE-2018-12127
CVE-2018-12130

(backported from commit 7c3658b2)
[juergh: Adjusted context.]
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/kernel/cpu/bugs.c

@@ -122,6 +122,8 @@ void __init check_bugs(void)
 
 	mds_select_mitigation();
 
+	arch_smt_update();
+
 #ifdef CONFIG_X86_32
 	/*
 	 * Check whether we are able to run this kernel safely on SMP.
@@ -510,8 +512,6 @@ static void __init spectre_v2_select_mitigation(void)
 		    mode != SPECTRE_V2_RETPOLINE_AMD)
 			set_ibrs_enabled(1);   /* Enable IBRS */
 	}
-
-	arch_smt_update();
 }
 
 /* Update the static key controlling the MDS CPU buffer clear in idle */