linux-kernel - [PATCH v2 1/2] x86/bugs: Use cpu_smt

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Message-Id: <20241031-x86_bugs_last_v2-v2-1-b7ff1dab840e@debian.org>
Date: Thu, 31 Oct 2024 04:06:16 -0700
From: Breno Leitao <leitao@...ian.org>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, 
 Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>, 
 Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, 
 Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, 
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
 Jonathan Corbet <corbet@....net>
Cc: linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
 Breno Leitao <leitao@...ian.org>
Subject: [PATCH v2 1/2] x86/bugs: Use cpu_smt_possible helper

There is a helper function to check if SMT is available. Use this helper
instead of performing the check manually.

The helper function cpu_smt_possible() does exactly the same thing as
was being done manually inside spectre_v2_user_select_mitigation().
Specifically, it returns false if CONFIG_SMP is disabled, otherwise
it checks the cpu_smt_control global variable.

This change improves code consistency and reduces duplication.

Signed-off-by: Breno Leitao <leitao@...ian.org>
Reviewed-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 47a01d4028f60e012d1e625e1667842b52948038..ceaa5f0c742025a62aa564aaa9cdfa1fe86e681c 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1332,16 +1332,11 @@ static void __init
 spectre_v2_user_select_mitigation(void)
 {
 	enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE;
-	bool smt_possible = IS_ENABLED(CONFIG_SMP);
 	enum spectre_v2_user_cmd cmd;

 	if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
 		return;

-	if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
-	    cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
-		smt_possible = false;
-
 	cmd = spectre_v2_parse_user_cmdline();
 	switch (cmd) {
 	case SPECTRE_V2_USER_CMD_NONE:
@@ -1402,7 +1397,7 @@ spectre_v2_user_select_mitigation(void)
 	 * so allow for STIBP to be selected in those cases.
 	 */
 	if (!boot_cpu_has(X86_FEATURE_STIBP) ||
-	    !smt_possible ||
+	    !cpu_smt_possible() ||
 	    (spectre_v2_in_eibrs_mode(spectre_v2_enabled) &&
 	     !boot_cpu_has(X86_FEATURE_AUTOIBRS)))
 		return;

-- 
2.43.5