Messages in this thread Patch in this message | | | Date | Wed, 09 Aug 2023 09:12:28 +0200 | From | Peter Zijlstra <> | Subject | [RFC][PATCH 10/17] x86: Remove CPU_IBPB_ENTRY |
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It was a pointless .config knob, it didn't even cause entry_ibpb to be omitted from the build.
Our Kconfig space is definitely too big to carry pointless ones.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/x86/Kconfig | 7 ------- arch/x86/include/asm/nospec-branch.h | 9 +++------ arch/x86/kernel/cpu/bugs.c | 18 +++++------------- 3 files changed, 8 insertions(+), 26 deletions(-)
--- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2577,13 +2577,6 @@ config CALL_THUNKS_DEBUG Only enable this when you are debugging call thunks as this creates a noticeable runtime overhead. If unsure say N. -config CPU_IBPB_ENTRY - bool "Enable IBPB on kernel entry" - depends on CPU_SUP_AMD && X86_64 - default y - help - Compile the kernel with support for the retbleed=ibpb mitigation. - config CPU_IBRS_ENTRY bool "Enable IBRS on kernel entry" depends on CPU_SUP_INTEL && X86_64 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -288,8 +288,7 @@ * where we have a stack but before any RET instruction. */ .macro UNTRAIN_RET -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CALL_DEPTH_TRACKING) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ @@ -299,8 +298,7 @@ .endm .macro UNTRAIN_RET_VM -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CALL_DEPTH_TRACKING) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ @@ -310,8 +308,7 @@ .endm .macro UNTRAIN_RET_FROM_CALL -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CALL_DEPTH_TRACKING) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -890,16 +890,13 @@ static void __init retbleed_select_mitig if (!boot_cpu_has(X86_FEATURE_IBPB)) { pr_err("WARNING: CPU does not support IBPB.\n"); goto do_cmd_auto; - } else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) { + } else { if (boot_cpu_has_bug(X86_BUG_SRSO) && !has_microcode) pr_err("IBPB-extending microcode not applied; SRSO NOT mitigated\n"); if (retbleed_cmd == RETBLEED_CMD_IBPB) retbleed_mitigation = RETBLEED_MITIGATION_IBPB; if (retbleed_cmd == RETBLEED_CMD_IBPB_VMEXIT) retbleed_mitigation = RETBLEED_MITIGATION_IBPB_VMEXIT; - } else { - pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n"); - goto do_cmd_auto; } break; @@ -932,7 +929,7 @@ static void __init retbleed_select_mitig retbleed_mitigation = RETBLEED_MITIGATION_UNRET_SRSO; } } - else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY) && boot_cpu_has(X86_FEATURE_IBPB)) + else if (boot_cpu_has(X86_FEATURE_IBPB)) retbleed_mitigation = RETBLEED_MITIGATION_IBPB; } @@ -2397,14 +2394,9 @@ static void __init srso_select_mitigatio break; case SRSO_CMD_IBPB: - if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) { - if (has_microcode) { - setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB); - srso_mitigation = SRSO_MITIGATION_IBPB; - } - } else { - pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n"); - goto pred_cmd; + if (has_microcode) { + setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB); + srso_mitigation = SRSO_MITIGATION_IBPB; } break;
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