From: Thadeu Lima de Souza Cascardo Date: Thu, 7 Jul 2022 16:41:52 +0000 (-0300) Subject: x86/bugs: Do not enable IBPB-on-entry when IBPB is not supported X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=3653093b7bbfa8c8c61858bffdc7f1e41ad436e1;p=linux.git x86/bugs: Do not enable IBPB-on-entry when IBPB is not supported commit 2259da159fbe5dba8ac00b560cf00b6a6537fa18 upstream. There are some VM configurations which have Skylake model but do not support IBPB. In those cases, when using retbleed=ibpb, userspace is going to be killed and kernel is going to panic. If the CPU does not support IBPB, warn and proceed with the auto option. Also, do not fallback to IBPB on AMD/Hygon systems if it is not supported. Fixes: 3ebc17006888 ("x86/bugs: Add retbleed=ibpb") Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Borislav Petkov Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 95219eb8e45cc..921d718e7f028 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -858,7 +858,10 @@ static void __init retbleed_select_mitigation(void) break; case RETBLEED_CMD_IBPB: - if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) { + 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)) { retbleed_mitigation = RETBLEED_MITIGATION_IBPB; } else { pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n"); @@ -873,7 +876,7 @@ do_cmd_auto: boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) { if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY)) retbleed_mitigation = RETBLEED_MITIGATION_UNRET; - else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) + else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY) && boot_cpu_has(X86_FEATURE_IBPB)) retbleed_mitigation = RETBLEED_MITIGATION_IBPB; }