From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: x86@kernel.org, Jon Kohler <jon@nutanix.com>,
Nikolay Borisov <nik.borisov@suse.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Josh Poimboeuf <jpoimboe@kernel.org>,
David Kaplan <david.kaplan@amd.com>,
Sean Christopherson <seanjc@google.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
KP Singh <kpsingh@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
David Laight <david.laight.linux@gmail.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
David Ahern <dsahern@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Asit Mallick <asit.k.mallick@intel.com>,
Tao Zhang <tao1.zhang@intel.com>,
bpf@vger.kernel.org, netdev@vger.kernel.org,
linux-doc@vger.kernel.org
Subject: [PATCH v8 03/10] x86/bhi: Rename clear_bhb_loop() to clear_bhb_loop_nofence()
Date: Tue, 24 Mar 2026 11:17:09 -0700 [thread overview]
Message-ID: <20260324-vmscape-bhb-v8-3-68bb524b3ab9@linux.intel.com> (raw)
In-Reply-To: <20260324-vmscape-bhb-v8-0-68bb524b3ab9@linux.intel.com>
To reflect the recent change that moved LFENCE to the caller side.
Suggested-by: Borislav Petkov <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
arch/x86/entry/entry_64.S | 8 ++++----
arch/x86/include/asm/nospec-branch.h | 6 +++---
arch/x86/net/bpf_jit_comp.c | 2 +-
3 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 8128e00ca73f..e9b81b95fcc8 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1532,7 +1532,7 @@ SYM_CODE_END(rewind_stack_and_make_dead)
* Note, callers should use a speculation barrier like LFENCE immediately after
* a call to this function to ensure BHB is cleared before indirect branches.
*/
-SYM_FUNC_START(clear_bhb_loop)
+SYM_FUNC_START(clear_bhb_loop_nofence)
ANNOTATE_NOENDBR
push %rbp
/* BPF caller may require %rax to be preserved */
@@ -1579,6 +1579,6 @@ SYM_FUNC_START(clear_bhb_loop)
pop %rax
pop %rbp
RET
-SYM_FUNC_END(clear_bhb_loop)
-EXPORT_SYMBOL_FOR_KVM(clear_bhb_loop)
-STACK_FRAME_NON_STANDARD(clear_bhb_loop)
+SYM_FUNC_END(clear_bhb_loop_nofence)
+EXPORT_SYMBOL_FOR_KVM(clear_bhb_loop_nofence)
+STACK_FRAME_NON_STANDARD(clear_bhb_loop_nofence)
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 70b377fcbc1c..0f5e6ed6c9c2 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -331,11 +331,11 @@
#ifdef CONFIG_X86_64
.macro CLEAR_BRANCH_HISTORY
- ALTERNATIVE "", "call clear_bhb_loop; lfence", X86_FEATURE_CLEAR_BHB_LOOP
+ ALTERNATIVE "", "call clear_bhb_loop_nofence; lfence", X86_FEATURE_CLEAR_BHB_LOOP
.endm
.macro CLEAR_BRANCH_HISTORY_VMEXIT
- ALTERNATIVE "", "call clear_bhb_loop; lfence", X86_FEATURE_CLEAR_BHB_VMEXIT
+ ALTERNATIVE "", "call clear_bhb_loop_nofence; lfence", X86_FEATURE_CLEAR_BHB_VMEXIT
.endm
#else
#define CLEAR_BRANCH_HISTORY
@@ -389,7 +389,7 @@ extern void entry_untrain_ret(void);
extern void write_ibpb(void);
#ifdef CONFIG_X86_64
-extern void clear_bhb_loop(void);
+extern void clear_bhb_loop_nofence(void);
#endif
extern void (*x86_return_thunk)(void);
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index e2cceabb23e8..b57e9ab51c5d 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1614,7 +1614,7 @@ static int emit_spectre_bhb_barrier(u8 **pprog, u8 *ip,
u8 *func;
if (cpu_feature_enabled(X86_FEATURE_CLEAR_BHB_LOOP)) {
- func = (u8 *)clear_bhb_loop;
+ func = (u8 *)clear_bhb_loop_nofence;
ip += x86_call_depth_emit_accounting(&prog, func, ip);
if (emit_call(&prog, func, ip))
--
2.34.1
next prev parent reply other threads:[~2026-03-24 18:17 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-24 18:16 [PATCH v8 00/10] VMSCAPE optimization for BHI variant Pawan Gupta
2026-03-24 18:16 ` [PATCH v8 01/10] x86/bhi: x86/vmscape: Move LFENCE out of clear_bhb_loop() Pawan Gupta
2026-03-24 20:22 ` Borislav Petkov
2026-03-24 21:30 ` Pawan Gupta
2026-03-24 18:16 ` [PATCH v8 02/10] x86/bhi: Make clear_bhb_loop() effective on newer CPUs Pawan Gupta
2026-03-24 20:59 ` Borislav Petkov
2026-03-24 22:13 ` Pawan Gupta
2026-03-25 20:37 ` Borislav Petkov
2026-03-25 22:40 ` David Laight
2026-03-26 8:39 ` Pawan Gupta
2026-03-26 9:15 ` David Laight
2026-03-26 10:01 ` Borislav Petkov
2026-03-26 10:45 ` David Laight
2026-03-26 20:29 ` Pawan Gupta
2026-03-25 17:50 ` Jim Mattson
2026-03-25 18:44 ` Pawan Gupta
2026-03-25 19:41 ` David Laight
2026-03-25 22:29 ` Pawan Gupta
2026-03-24 18:17 ` Pawan Gupta [this message]
2026-03-24 18:17 ` [PATCH v8 04/10] x86/vmscape: Rename x86_ibpb_exit_to_user to x86_predictor_flush_exit_to_user Pawan Gupta
2026-03-24 18:17 ` [PATCH v8 05/10] x86/vmscape: Move mitigation selection to a switch() Pawan Gupta
2026-03-24 18:17 ` [PATCH v8 06/10] x86/vmscape: Use write_ibpb() instead of indirect_branch_prediction_barrier() Pawan Gupta
2026-03-24 18:18 ` [PATCH v8 07/10] x86/vmscape: Use static_call() for predictor flush Pawan Gupta
2026-03-24 19:09 ` bot+bpf-ci
2026-03-24 19:51 ` Pawan Gupta
2026-03-24 18:18 ` [PATCH v8 08/10] x86/vmscape: Deploy BHB clearing mitigation Pawan Gupta
2026-03-24 19:09 ` bot+bpf-ci
2026-03-24 19:46 ` Pawan Gupta
2026-03-24 18:18 ` [PATCH v8 09/10] x86/vmscape: Resolve conflict between attack-vectors and vmscape=force Pawan Gupta
2026-03-24 18:19 ` [PATCH v8 10/10] x86/vmscape: Add cmdline vmscape=on to override attack vector controls Pawan Gupta
2026-03-24 19:09 ` bot+bpf-ci
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