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authorJohannes Wikner <kwikner@ethz.ch>2024-09-23 20:49:34 +0200
committerBorislav Petkov (AMD) <bp@alien8.de>2024-10-10 10:34:29 +0200
commit3ea87dfa31a7b0bb0ff1675e67b9e54883013074 (patch)
tree5e2d4b48d1427405de974b93921ce54fa428eb56 /arch
parentff898623af2ed564300752bba83a680a1e4fec8d (diff)
x86/cpufeatures: Add a IBPB_NO_RET BUG flag
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 <kwikner@ethz.ch> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Cc: <stable@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/include/asm/cpufeatures.h1
-rw-r--r--arch/x86/kernel/cpu/common.c3
2 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index a222a24677d7..913fd3a7bac6 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -524,4 +524,5 @@
#define X86_BUG_DIV0 X86_BUG(1*32 + 1) /* "div0" AMD DIV0 speculation bug */
#define X86_BUG_RFDS X86_BUG(1*32 + 2) /* "rfds" CPU is vulnerable to Register File Data Sampling */
#define X86_BUG_BHI X86_BUG(1*32 + 3) /* "bhi" 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 07a34d723505..f1040cb64841 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1443,6 +1443,9 @@ 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;