6.16-stable review patch. If anyone has any objections, please let me know.
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From: Pawan Gupta pawan.kumar.gupta@linux.intel.com
[ Upstream commit 98ff5c071d1cde9426b0bfa449c43d49ec58f1c4 ]
The retbleed select function leaves the mitigation to AUTO in some cases. Moreover, the update function can also set the mitigation to AUTO. This is inconsistent with other mitigations and requires explicit handling of AUTO at the end of update step.
Make sure a mitigation gets selected in the select step, and do not change it to AUTO in the update step. When no mitigation can be selected leave it to NONE, which is what AUTO was getting changed to in the end.
Suggested-by: Borislav Petkov bp@alien8.de Signed-off-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Acked-by: Borislav Petkov (AMD) bp@alien8.de Link: https://lore.kernel.org/20250611-eibrs-fix-v4-1-5ff86cac6c61@linux.intel.com Stable-dep-of: ab9f2388e0b9 ("x86/bugs: Allow ITS stuffing in eIBRS+retpoline mode also") Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/cpu/bugs.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index f4d3abb12317..0bf2566d21b6 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1251,6 +1251,14 @@ static void __init retbleed_select_mitigation(void) retbleed_mitigation = RETBLEED_MITIGATION_IBPB; else retbleed_mitigation = RETBLEED_MITIGATION_NONE; + } else if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) { + /* Final mitigation depends on spectre-v2 selection */ + if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) + retbleed_mitigation = RETBLEED_MITIGATION_EIBRS; + else if (boot_cpu_has(X86_FEATURE_IBRS)) + retbleed_mitigation = RETBLEED_MITIGATION_IBRS; + else + retbleed_mitigation = RETBLEED_MITIGATION_NONE; } }
@@ -1259,9 +1267,6 @@ static void __init retbleed_update_mitigation(void) if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off()) return;
- if (retbleed_mitigation == RETBLEED_MITIGATION_NONE) - goto out; - /* * retbleed=stuff is only allowed on Intel. If stuffing can't be used * then a different mitigation will be selected below. @@ -1272,7 +1277,7 @@ static void __init retbleed_update_mitigation(void) its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF) { if (spectre_v2_enabled != SPECTRE_V2_RETPOLINE) { pr_err("WARNING: retbleed=stuff depends on spectre_v2=retpoline\n"); - retbleed_mitigation = RETBLEED_MITIGATION_AUTO; + retbleed_mitigation = RETBLEED_MITIGATION_NONE; } else { if (retbleed_mitigation != RETBLEED_MITIGATION_STUFF) pr_info("Retbleed mitigation updated to stuffing\n"); @@ -1298,15 +1303,11 @@ static void __init retbleed_update_mitigation(void) if (retbleed_mitigation != RETBLEED_MITIGATION_STUFF) pr_err(RETBLEED_INTEL_MSG); } - /* If nothing has set the mitigation yet, default to NONE. */ - if (retbleed_mitigation == RETBLEED_MITIGATION_AUTO) - retbleed_mitigation = RETBLEED_MITIGATION_NONE; } -out: + pr_info("%s\n", retbleed_strings[retbleed_mitigation]); }
- static void __init retbleed_apply_mitigation(void) { bool mitigate_smt = false;