Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Cross-merge bpf fixes after downstream PR.

No conflicts.

Adjacent changes in:

include/linux/bpf.h
include/uapi/linux/bpf.h
kernel/bpf/btf.c
kernel/bpf/helpers.c
kernel/bpf/syscall.c
kernel/bpf/verifier.c
kernel/trace/bpf_trace.c
mm/slab_common.c
tools/include/uapi/linux/bpf.h
tools/testing/selftests/bpf/Makefile

Link: https://lore.kernel.org/all/20241024215724.60017-1-daniel@iogearbox.net/
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d1915427b4ff..47a01d4028f6 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1115,8 +1115,25 @@ do_cmd_auto:
 
 	case RETBLEED_MITIGATION_IBPB:
 		setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB);
+
+		/*
+		 * IBPB on entry already obviates the need for
+		 * software-based untraining so clear those in case some
+		 * other mitigation like SRSO has selected them.
+		 */
+		setup_clear_cpu_cap(X86_FEATURE_UNRET);
+		setup_clear_cpu_cap(X86_FEATURE_RETHUNK);
+
 		setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT);
 		mitigate_smt = true;
+
+		/*
+		 * There is no need for RSB filling: entry_ibpb() ensures
+		 * all predictions, including the RSB, are invalidated,
+		 * regardless of IBPB implementation.
+		 */
+		setup_clear_cpu_cap(X86_FEATURE_RSB_VMEXIT);
+
 		break;
 
 	case RETBLEED_MITIGATION_STUFF:
@@ -2627,6 +2644,14 @@ static void __init srso_select_mitigation(void)
 			if (has_microcode) {
 				setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB);
 				srso_mitigation = SRSO_MITIGATION_IBPB;
+
+				/*
+				 * IBPB on entry already obviates the need for
+				 * software-based untraining so clear those in case some
+				 * other mitigation like Retbleed has selected them.
+				 */
+				setup_clear_cpu_cap(X86_FEATURE_UNRET);
+				setup_clear_cpu_cap(X86_FEATURE_RETHUNK);
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with MITIGATION_IBPB_ENTRY.\n");
@@ -2638,6 +2663,13 @@ static void __init srso_select_mitigation(void)
 			if (!boot_cpu_has(X86_FEATURE_ENTRY_IBPB) && has_microcode) {
 				setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT);
 				srso_mitigation = SRSO_MITIGATION_IBPB_ON_VMEXIT;
+
+				/*
+				 * There is no need for RSB filling: entry_ibpb() ensures
+				 * all predictions, including the RSB, are invalidated,
+				 * regardless of IBPB implementation.
+				 */
+				setup_clear_cpu_cap(X86_FEATURE_RSB_VMEXIT);
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with MITIGATION_SRSO.\n");