linux-kernel - [PATCH v5 15/20] x86/bugs: Add attack vector controls for spectre

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Message-ID: <20250509162839.3057217-16-david.kaplan@amd.com>
Date: Fri, 9 May 2025 11:28:34 -0500
From: David Kaplan <david.kaplan@....com>
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>
CC: <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 15/20] x86/bugs: Add attack vector controls for spectre_v2

Use attack vector controls to determine if spectre_v2 mitigation is
required.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/cpu/bugs.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 667385808400..6a4bc80be1e9 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1728,8 +1728,7 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 	int ret, i;
 
 	cmd = IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ?  SPECTRE_V2_CMD_AUTO : SPECTRE_V2_CMD_NONE;
-	if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") ||
-	    cpu_mitigations_off())
+	if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
 		return SPECTRE_V2_CMD_NONE;
 
 	ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
@@ -2008,8 +2007,11 @@ static void __init spectre_v2_select_mitigation(void)
 	case SPECTRE_V2_CMD_NONE:
 		return;
 
-	case SPECTRE_V2_CMD_FORCE:
 	case SPECTRE_V2_CMD_AUTO:
+		if (!should_mitigate_vuln(X86_BUG_SPECTRE_V2))
+			break;
+		fallthrough;
+	case SPECTRE_V2_CMD_FORCE:
 		if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
 			spectre_v2_enabled = SPECTRE_V2_EIBRS;
 			break;
@@ -2062,7 +2064,7 @@ static void __init spectre_v2_update_mitigation(void)
 		}
 	}
 
-	if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) && !cpu_mitigations_off())
+	if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
 		pr_info("%s\n", spectre_v2_strings[spectre_v2_enabled]);
 }
 
-- 
2.34.1