x86/speculation: Merge one test in spectre_v2_user_select_mitigation()

stable inclusion
from stable-v4.19.234
commit d86fc674172edc0794f84198405f59f00b71512a
category: bugfix
bugzilla: 186453, https://gitee.com/src-openeuler/kernel/issues/I50WBM
CVE: CVE-2022-0001

--------------------------------

commit a5ce9f2b upstream.

Merge the test whether the CPU supports STIBP into the test which
determines whether STIBP is required. Thus try to simplify what is
already an insane logic.

Remove a superfluous newline in a comment, while at it.
Signed-off-by: NBorislav Petkov <bp@suse.de>
Cc: Anthony Steinhauser <asteinhauser@google.com>
Link: https://lkml.kernel.org/r/20200615065806.GB14668@zn.tnic
[fllinden@amazon.com: fixed contextual conflict (comment) for 4.19]
Signed-off-by: NFrank van der Linden <fllinden@amazon.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Conflicts:
    arch/x85/kernel/cpu/bugs.c
Signed-off-by: NChen Jiahao <chenjiahao16@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Reviewed-by: NLiao Chang <liaochang1@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

arch/x86/kernel/cpu/bugs.c

@@ -756,10 +756,12 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 	}
 
 	/*
-	 * If enhanced IBRS is enabled or SMT impossible, STIBP is not
+	 * If no STIBP, enhanced IBRS is enabled or SMT impossible, STIBP is not
 	 * required.
 	 */
-	if (!smt_possible || spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+	if (!boot_cpu_has(X86_FEATURE_STIBP) ||
+	    !smt_possible ||
+	    spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
 		return;
 
 	/*
@@ -771,12 +773,6 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 	    boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
 		mode = SPECTRE_V2_USER_STRICT_PREFERRED;
 
-	/*
-	 * If STIBP is not available, clear the STIBP mode.
-	 */
-	if (!boot_cpu_has(X86_FEATURE_STIBP))
-		mode = SPECTRE_V2_USER_NONE;
-
 	spectre_v2_user_stibp = mode;
 
 set_mode: