[tip: x86/bugs] x86/bugs: Add attack vector controls for spectre_v2_user

["tip-bot2 for David Kaplan" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     07a659edcf6eb56f7906fc415f46e3a7f37d5383
Gitweb:        https://git.kernel.org/tip/07a659edcf6eb56f7906fc415f46e3a7f37d5383
Author:        David Kaplan <david.kaplan@amd.com>
AuthorDate:    Mon, 07 Jul 2025 13:33:08 -05:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 11 Jul 2025 17:56:41 +02:00

x86/bugs: Add attack vector controls for spectre_v2_user

Use attack vector controls to determine if spectre_v2_user mitigation is
required.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250707183316.1349127-14-david.kaplan@amd.com
---
 arch/x86/kernel/cpu/bugs.c |  9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index de6eb59..ff56251 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1817,7 +1817,7 @@ static enum spectre_v2_user_cmd __init spectre_v2_parse_user_cmdline(void)
 	char arg[20];
 	int ret, i;
 
-	if (cpu_mitigations_off() || !IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2))
+	if (!IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2))
 		return SPECTRE_V2_USER_CMD_NONE;
 
 	ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
@@ -1855,6 +1855,13 @@ static void __init spectre_v2_user_select_mitigation(void)
 		spectre_v2_user_stibp = SPECTRE_V2_USER_STRICT;
 		break;
 	case SPECTRE_V2_USER_CMD_AUTO:
+		if (!should_mitigate_vuln(X86_BUG_SPECTRE_V2_USER))
+			break;
+		spectre_v2_user_ibpb = SPECTRE_V2_USER_PRCTL;
+		if (smt_mitigations == SMT_MITIGATIONS_OFF)
+			break;
+		spectre_v2_user_stibp = SPECTRE_V2_USER_PRCTL;
+		break;
 	case SPECTRE_V2_USER_CMD_PRCTL:
 		spectre_v2_user_ibpb  = SPECTRE_V2_USER_PRCTL;
 		spectre_v2_user_stibp = SPECTRE_V2_USER_PRCTL;