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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 06/10] x86/vmscape: Use write_ibpb() instead of indirect_branch_prediction_barrier()
Date: Tue, 24 Mar 2026 11:17:58 -0700	[thread overview]
Message-ID: <20260324-vmscape-bhb-v8-6-68bb524b3ab9@linux.intel.com> (raw)
In-Reply-To: <20260324-vmscape-bhb-v8-0-68bb524b3ab9@linux.intel.com>

indirect_branch_prediction_barrier() is a wrapper to write_ibpb(), which
also checks if the CPU supports IBPB. For VMSCAPE, call to
indirect_branch_prediction_barrier() is only possible when CPU supports
IBPB.

Simply call write_ibpb() directly to avoid unnecessary alternative
patching.

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
 arch/x86/include/asm/entry-common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h
index c45858db16c9..78b143673ca7 100644
--- a/arch/x86/include/asm/entry-common.h
+++ b/arch/x86/include/asm/entry-common.h
@@ -97,7 +97,7 @@ static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
 	/* Avoid unnecessary reads of 'x86_predictor_flush_exit_to_user' */
 	if (cpu_feature_enabled(X86_FEATURE_IBPB_EXIT_TO_USER) &&
 	    this_cpu_read(x86_predictor_flush_exit_to_user)) {
-		indirect_branch_prediction_barrier();
+		write_ibpb();
 		this_cpu_write(x86_predictor_flush_exit_to_user, false);
 	}
 }

-- 
2.34.1



  parent reply	other threads:[~2026-03-24 18:17 UTC|newest]

Thread overview: 30+ 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
2026-03-25 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 ` [PATCH v8 03/10] x86/bhi: Rename clear_bhb_loop() to clear_bhb_loop_nofence() Pawan Gupta
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 ` Pawan Gupta [this message]
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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