x86/bugs: Fix handling when SRSO mitigation is disabled

[ Upstream commit 1dbb6b1495d472806fef1f4c94f5b3e4c89a3c1d ]

When the SRSO mitigation is disabled, either via mitigations=off or
spec_rstack_overflow=off, the warning about the lack of IBPB-enhancing
microcode is printed anyway.

This is unnecessary since the user has turned off the mitigation.

  [ bp: Massage, drop SBPB rationale as it doesn't matter because when
    mitigations are disabled x86_pred_cmd is not being used anyway. ]

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20240904150711.193022-1-david.kaplan@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b6f927f6c567e1a0086f5b31ea86abd1ea6af84f..47c84503ad9be7cd78a5002e0d116602f665d3f9 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2545,10 +2545,9 @@ static void __init srso_select_mitigation(void)
 {
        bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
-       if (cpu_mitigations_off())
-               return;
-
-       if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
+       if (!boot_cpu_has_bug(X86_BUG_SRSO) ||
+           cpu_mitigations_off() ||
+           srso_cmd == SRSO_CMD_OFF) {
                if (boot_cpu_has(X86_FEATURE_SBPB))
                        x86_pred_cmd = PRED_CMD_SBPB;
                return;
@@ -2579,11 +2578,6 @@ static void __init srso_select_mitigation(void)
        }
 
        switch (srso_cmd) {
-       case SRSO_CMD_OFF:
-               if (boot_cpu_has(X86_FEATURE_SBPB))
-                       x86_pred_cmd = PRED_CMD_SBPB;
-               return;
-
        case SRSO_CMD_MICROCODE:
                if (has_microcode) {
                        srso_mitigation = SRSO_MITIGATION_MICROCODE;
@@ -2637,6 +2631,8 @@ static void __init srso_select_mitigation(void)
                        pr_err("WARNING: kernel not compiled with MITIGATION_SRSO.\n");
                 }
                break;
+       default:
+               break;
        }
 
 out: