From 1e0398acb650933b21b97fe768ca13e372ff77d7 Mon Sep 17 00:00:00 2001 From: Johannes Wikner Date: Mon, 23 Sep 2024 20:49:34 +0200 Subject: [PATCH] x86/cpufeatures: Add a IBPB_NO_RET BUG flag commit 3ea87dfa31a7b0bb0ff1675e67b9e54883013074 upstream. Set this flag if the CPU has an IBPB implementation that does not invalidate return target predictions. Zen generations < 4 do not flush the RSB when executing an IBPB and this bug flag denotes that. [ bp: Massage. ] Signed-off-by: Johannes Wikner Signed-off-by: Borislav Petkov (AMD) Cc: Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/kernel/cpu/common.c | 3 +++ 2 files changed, 4 insertions(+) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index e25a0a2529f7..3c0f7e332478 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -481,4 +481,5 @@ #define X86_BUG_DIV0 X86_BUG(1*32 + 1) /* AMD DIV0 speculation bug */ #define X86_BUG_RFDS X86_BUG(1*32 + 2) /* CPU is vulnerable to Register File Data Sampling */ #define X86_BUG_BHI X86_BUG(1*32 + 3) /* CPU is affected by Branch History Injection */ +#define X86_BUG_IBPB_NO_RET X86_BUG(1*32 + 4) /* "ibpb_no_ret" IBPB omits return target predictions */ #endif /* _ASM_X86_CPUFEATURES_H */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 809e12f130d8..f0cc4c616ceb 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1352,6 +1352,9 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c) boot_cpu_has(X86_FEATURE_HYPERVISOR))) setup_force_cpu_bug(X86_BUG_BHI); + if (cpu_has(c, X86_FEATURE_AMD_IBPB) && !cpu_has(c, X86_FEATURE_AMD_IBPB_RET)) + setup_force_cpu_bug(X86_BUG_IBPB_NO_RET); + if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN)) return;