For retbleed=ibpb, force STIBP on machines that have it,
and report its SMT vulnerability status accordingly.
Fixes: 3ebc17006888 ("x86/bugs: Add retbleed=ibpb")
Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 4 +++-
arch/x86/kernel/cpu/bugs.c | 10 ++++++----
2 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 597ac77b541c..127fa4328360 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5212,10 +5212,12 @@
ibpb - mitigate short speculation windows on
basic block boundaries too. Safe, highest
perf impact.
+ ibpb,nosmt - like ibpb, but will disable SMT when STIBP
+ is not available.
unret - force enable untrained return thunks,
only effective on AMD f15h-f17h
based systems.
- unret,nosmt - like unret, will disable SMT when STIBP
+ unret,nosmt - like unret, but will disable SMT when STIBP
is not available.
Selecting 'auto' will choose a mitigation method at run
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index fd5464ff714d..f710c012f1eb 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -152,7 +152,7 @@ void __init check_bugs(void)
/*
* spectre_v2_user_select_mitigation() relies on the state set by
* retbleed_select_mitigation(); specifically the STIBP selection is
- * forced for UNRET.
+ * forced for UNRET or IBPB.
*/
spectre_v2_user_select_mitigation();
ssb_select_mitigation();
@@ -1181,7 +1181,8 @@ spectre_v2_user_select_mitigation(void)
boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
mode = SPECTRE_V2_USER_STRICT_PREFERRED;
- if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET) {
+ if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET ||
+ retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
if (mode != SPECTRE_V2_USER_STRICT &&
mode != SPECTRE_V2_USER_STRICT_PREFERRED)
pr_info("Selecting STIBP always-on mode to complement retbleed mitigation\n");
@@ -2346,10 +2347,11 @@ static ssize_t srbds_show_state(char *buf)
static ssize_t retbleed_show_state(char *buf)
{
- if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET) {
+ if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET ||
+ retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
- return sprintf(buf, "Vulnerable: untrained return thunk on non-Zen uarch\n");
+ return sprintf(buf, "Vulnerable: untrained return thunk / IBPB on non-AMD based uarch\n");
return sprintf(buf, "%s; SMT %s\n",
retbleed_strings[retbleed_mitigation],
--
2.34.1
