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From: Yosry Ahmed <yosry.ahmed@linux.dev>
To: x86@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/6] x86/mm: Remove X86_FEATURE_USE_IBPB checks in cond_mitigation()
Date: Wed, 19 Feb 2025 22:08:22 +0000	[thread overview]
Message-ID: <20250219220826.2453186-3-yosry.ahmed@linux.dev> (raw)
In-Reply-To: <20250219220826.2453186-1-yosry.ahmed@linux.dev>

The check is performed when either switch_mm_cond_ibpb or
switch_mm_always_ibpb is set. In both cases, X86_FEATURE_USE_IBPB is
always set. Remove the redundant check.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
---
 arch/x86/mm/tlb.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index be0c1a509869c..e860fc8edfae4 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -437,8 +437,7 @@ static void cond_mitigation(struct task_struct *next)
 		 * both have the IBPB bit set.
 		 */
 		if (next_mm != prev_mm &&
-		    (next_mm | prev_mm) & LAST_USER_MM_IBPB &&
-		    cpu_feature_enabled(X86_FEATURE_USE_IBPB))
+		    (next_mm | prev_mm) & LAST_USER_MM_IBPB)
 			indirect_branch_prediction_barrier();
 	}
 
@@ -448,8 +447,7 @@ static void cond_mitigation(struct task_struct *next)
 		 * different context than the user space task which ran
 		 * last on this CPU.
 		 */
-		if ((prev_mm & ~LAST_USER_MM_SPEC_MASK) != (unsigned long)next->mm &&
-		    cpu_feature_enabled(X86_FEATURE_USE_IBPB))
+		if ((prev_mm & ~LAST_USER_MM_SPEC_MASK) != (unsigned long)next->mm)
 			indirect_branch_prediction_barrier();
 	}
 
-- 
2.48.1.601.g30ceb7b040-goog


  parent reply	other threads:[~2025-02-19 22:08 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-02-19 22:08 [PATCH 0/6] IBPB cleanups and a fixup Yosry Ahmed
2025-02-19 22:08 ` [PATCH 1/6] x86/bugs: Move the X86_FEATURE_USE_IBPB check into callers Yosry Ahmed
2025-02-25 19:47   ` Sean Christopherson
2025-02-25 21:28     ` Yosry Ahmed
2025-02-19 22:08 ` Yosry Ahmed [this message]
2025-02-19 22:08 ` [PATCH 3/6] x86/bugs: Remove the X86_FEATURE_USE_IBPB check in ib_prctl_set() Yosry Ahmed
2025-02-19 22:08 ` [PATCH 4/6] x86/bugs: Use a static branch to guard IBPB on vCPU load Yosry Ahmed
2025-02-25 19:49   ` Sean Christopherson
2025-02-25 21:27     ` Yosry Ahmed
2025-02-25 22:40       ` Sean Christopherson
2025-02-26  2:49         ` Yosry Ahmed
2025-02-27  0:46           ` Sean Christopherson
2025-02-27  0:54             ` Yosry Ahmed
2025-02-19 22:08 ` [PATCH 5/6] KVM: nVMX: Always use IBPB to properly virtualize IBRS Yosry Ahmed
2025-02-19 23:09   ` Jim Mattson
2025-02-25 19:50   ` Sean Christopherson
2025-02-19 22:08 ` [PATCH 6/6] x86/bugs: Remove X86_FEATURE_USE_IBPB Yosry Ahmed
2025-02-20 19:04 ` [PATCH 0/6] IBPB cleanups and a fixup Josh Poimboeuf
2025-02-20 19:59   ` Yosry Ahmed
2025-02-20 20:47     ` Josh Poimboeuf
2025-02-20 21:50       ` Yosry Ahmed

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