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From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: x86@kernel.org, David Kaplan <david.kaplan@amd.com>,
	Nikolay Borisov <nik.borisov@suse.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Asit Mallick <asit.k.mallick@intel.com>,
	Tao Zhang <tao1.zhang@intel.com>
Subject: [PATCH v4 07/11] x86/vmscape: Use write_ibpb() instead of indirect_branch_prediction_barrier()
Date: Wed, 19 Nov 2025 22:19:19 -0800	[thread overview]
Message-ID: <20251119-vmscape-bhb-v4-7-1adad4e69ddc@linux.intel.com> (raw)
In-Reply-To: <20251119-vmscape-bhb-v4-0-1adad4e69ddc@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>
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 c45858db16c92fc1364fb818185fba7657840991..78b143673ca72642149eb2dbf3e3e31370fe6b28 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:[~2025-11-20  6:19 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-20  6:17 [PATCH v4 00/11] VMSCAPE optimization for BHI variant Pawan Gupta
2025-11-20  6:17 ` [PATCH v4 01/11] x86/bhi: x86/vmscape: Move LFENCE out of clear_bhb_loop() Pawan Gupta
2025-11-20 16:15   ` Nikolay Borisov
2025-11-20 16:56     ` Pawan Gupta
2025-11-20 16:58       ` Nikolay Borisov
2025-11-20  6:18 ` [PATCH v4 02/11] x86/bhi: Move the BHB sequence to a macro for reuse Pawan Gupta
2025-11-20 16:28   ` Nikolay Borisov
2025-11-20 16:57     ` Pawan Gupta
2025-11-25  0:21   ` Pawan Gupta
2025-11-20  6:18 ` [PATCH v4 03/11] x86/bhi: Make the depth of BHB-clearing configurable Pawan Gupta
2025-11-20 17:02   ` Nikolay Borisov
2025-11-20  6:18 ` [PATCH v4 04/11] x86/bhi: Make clear_bhb_loop() effective on newer CPUs Pawan Gupta
2025-11-21 12:33   ` Nikolay Borisov
2025-11-21 16:40   ` Dave Hansen
2025-11-21 16:45     ` Nikolay Borisov
2025-11-21 16:50       ` Dave Hansen
2025-11-21 18:16         ` Pawan Gupta
2025-11-21 18:42           ` Dave Hansen
2025-11-21 21:26             ` Pawan Gupta
2025-11-21 21:36               ` Dave Hansen
2025-11-24 19:21                 ` Pawan Gupta
2025-11-22 11:05               ` david laight
2025-11-24 19:31                 ` Pawan Gupta
2025-11-25 11:34                   ` david laight
2025-12-04  1:40                     ` Pawan Gupta
2025-12-04  9:15                       ` david laight
2025-12-04 21:56                         ` Pawan Gupta
2025-12-05  9:21                           ` david laight
2025-11-26 19:23     ` Pawan Gupta
2026-03-06 21:00   ` Jim Mattson
2026-03-06 22:32     ` Pawan Gupta
2026-03-06 22:57       ` Jim Mattson
2026-03-06 23:29         ` Pawan Gupta
2026-03-07  0:35           ` Jim Mattson
2026-03-07  1:00             ` Pawan Gupta
2026-03-07  1:10               ` Jim Mattson
2026-03-07  2:41                 ` Pawan Gupta
2026-03-07  5:05                   ` Jim Mattson
2026-03-09 22:29                     ` Pawan Gupta
2026-03-09 23:05                       ` Jim Mattson
2026-03-10  0:00                         ` Pawan Gupta
2026-03-10  0:08                           ` Jim Mattson
2026-03-10  0:52                             ` Pawan Gupta
2025-11-20  6:18 ` [PATCH v4 05/11] x86/vmscape: Rename x86_ibpb_exit_to_user to x86_predictor_flush_exit_to_user Pawan Gupta
2025-11-20  6:19 ` [PATCH v4 06/11] x86/vmscape: Move mitigation selection to a switch() Pawan Gupta
2025-11-21 14:27   ` Nikolay Borisov
2025-11-24 23:09     ` Pawan Gupta
2025-11-25 10:19       ` Nikolay Borisov
2025-11-25 17:45         ` Pawan Gupta
2025-11-20  6:19 ` Pawan Gupta [this message]
2025-11-21 12:59   ` [PATCH v4 07/11] x86/vmscape: Use write_ibpb() instead of indirect_branch_prediction_barrier() Nikolay Borisov
2025-11-20  6:19 ` [PATCH v4 08/11] x86/vmscape: Use static_call() for predictor flush Pawan Gupta
2025-11-20  6:19 ` [PATCH v4 09/11] x86/vmscape: Deploy BHB clearing mitigation Pawan Gupta
2025-11-21 14:18   ` Nikolay Borisov
2025-11-21 18:29     ` Pawan Gupta
2025-11-21 14:23   ` Nikolay Borisov
2025-11-21 18:41     ` Pawan Gupta
2025-11-21 18:53       ` Nikolay Borisov
2025-11-21 21:29         ` Pawan Gupta
2025-11-20  6:20 ` [PATCH v4 10/11] x86/vmscape: Override conflicting attack-vector controls with =force Pawan Gupta
2025-11-21 18:04   ` Nikolay Borisov
2025-11-20  6:20 ` [PATCH v4 11/11] x86/vmscape: Add cmdline vmscape=on to override attack vector controls Pawan Gupta
2025-11-25 11:41   ` Nikolay Borisov

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