x86/srso: Correct the mitigation status when SMT is disabled

Specify how is SRSO mitigated when SMT is disabled. Also, correct the
SMT check for that.

Fixes: e9fbc47 ("x86/srso: Disable the mitigation on unaffected configurations")
Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20230814200813.p5czl47zssuej7nv@treble

CVE-2023-20569
(cherry picked from commit 6405b72)
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Acked-by: Roxana Nicolescu <roxana.nicolescu@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

@@ -2428,8 +2428,7 @@ static void __init srso_select_mitigation(void)
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
 		 */
-		if ((boot_cpu_data.x86 < 0x19) &&
-		    (!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED))) {
+		if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
 			return;
 		}
@@ -2713,7 +2712,7 @@ static ssize_t retbleed_show_state(char *buf)
 static ssize_t srso_show_state(char *buf)
 {
 	if (boot_cpu_has(X86_FEATURE_SRSO_NO))
-		return sysfs_emit(buf, "Not affected\n");
+		return sysfs_emit(buf, "Mitigation: SMT disabled\n");
 
 	return sysfs_emit(buf, "%s%s\n",
 			  srso_strings[srso_mitigation],