x86/bugs: Remove its=stuff dependency on retbleed

Allow ITS to enable stuffing independent of retbleed. The dependency is only
on retpoline. It is a valid case for retbleed to be mitigated by eIBRS while
ITS deploys stuffing at the same time.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250611-eibrs-fix-v4-6-5ff86cac6c61@linux.intel.com

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 387610ad222d4dbd196bfb219145510a37979d73..31f3db0a514ea3d6e2513c0f6e072b84e0117f08 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1467,13 +1467,8 @@ static void __init its_update_mitigation(void)
                break;
        }
 
-       /*
-        * retbleed_update_mitigation() will try to do stuffing if its=stuff.
-        * If it can't, such as if spectre_v2!=retpoline, then fall back to
-        * aligned thunks.
-        */
        if (its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF &&
-           retbleed_mitigation != RETBLEED_MITIGATION_STUFF)
+           !cdt_possible(spectre_v2_enabled))
                its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;
 
        pr_info("%s\n", its_strings[its_mitigation]);
@@ -1485,8 +1480,6 @@ static void __init its_apply_mitigation(void)
        case ITS_MITIGATION_OFF:
        case ITS_MITIGATION_AUTO:
        case ITS_MITIGATION_VMEXIT_ONLY:
-       /* its=stuff forces retbleed stuffing and is enabled there. */
-       case ITS_MITIGATION_RETPOLINE_STUFF:
                break;
        case ITS_MITIGATION_ALIGNED_THUNKS:
                if (!boot_cpu_has(X86_FEATURE_RETPOLINE))
@@ -1495,6 +1488,11 @@ static void __init its_apply_mitigation(void)
                setup_force_cpu_cap(X86_FEATURE_RETHUNK);
                set_return_thunk(its_return_thunk);
                break;
+       case ITS_MITIGATION_RETPOLINE_STUFF:
+               setup_force_cpu_cap(X86_FEATURE_RETHUNK);
+               setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);
+               set_return_thunk(call_depth_return_thunk);
+               break;
        }
 }