The following commit has been merged into the x86/bugs branch of tip:
Commit-ID: 8374a2719df2a00781e6821e373d7de71390d1b4
Gitweb: https://git.kernel.org/tip/8374a2719df2a00781e6821e373d7de71390d1b4
Author: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
AuthorDate: Wed, 11 Jun 2025 10:30:03 -07:00
Committer: Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Mon, 23 Jun 2025 12:26:57 +02:00
x86/bugs: Introduce cdt_possible()
In preparation to allow ITS to also enable stuffing aka Call Depth
Tracking (CDT) independently of retbleed, introduce a helper
cdt_possible().
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-v4-5-5ff86cac6c61@linux.intel.com
---
arch/x86/kernel/cpu/bugs.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e861e88..387610a 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1119,6 +1119,19 @@ early_param("nospectre_v1", nospectre_v1_cmdline);
enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init = SPECTRE_V2_NONE;
+/* Depends on spectre_v2 mitigation selected already */
+static inline bool cdt_possible(enum spectre_v2_mitigation mode)
+{
+ if (!IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING) ||
+ !IS_ENABLED(CONFIG_MITIGATION_RETPOLINE))
+ return false;
+
+ if (mode == SPECTRE_V2_RETPOLINE)
+ return true;
+
+ return false;
+}
+
#undef pr_fmt
#define pr_fmt(fmt) "RETBleed: " fmt
@@ -1267,7 +1280,7 @@ static void __init retbleed_update_mitigation(void)
retbleed_mitigation = RETBLEED_MITIGATION_STUFF;
if (retbleed_mitigation == RETBLEED_MITIGATION_STUFF &&
- spectre_v2_enabled != SPECTRE_V2_RETPOLINE) {
+ !cdt_possible(spectre_v2_enabled)) {
pr_err("WARNING: retbleed=stuff depends on spectre_v2=retpoline\n");
retbleed_mitigation = RETBLEED_MITIGATION_NONE;
}