From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B0493C433EF for ; Thu, 27 Jan 2022 19:26:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=Zn9XbinbS8ed9DGX4mznPpUTJaYtYyBn+GgiwgQ3j20=; b=mnbarwvXLQXXqn 1U0hnMIZbTDbChOuxhEy7BiZ+z04aL3vPOTqIIDCNGegta1W7daw/M/a6fsq1Ke91Aux5hMP6vAtY OOm853CTydFqAKkeGOZD4iDNTZa64uTDrM8h1bRnA4XhF1y4XE4mtjlD+2RwXu1VkYWWrMJoicd7x GTVrfvzDBoFtDon7h+xfdOV6ihdS9tXnhir6r02ailkC46MjadFfkwz5v2b1Hb6hAI9tCrKOZuyS8 Ffj9Hp3rP7nXDmytzRieDA+Zcuh3lYCR7r5oDE+WonSZUZwRp1yd4jkmLGpmiZsYnlkeaIqFKmjpx TiTArGhoKf+gcKWizAfQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nDAOE-00GvxO-1T; Thu, 27 Jan 2022 19:25:02 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nDAOA-00GvwP-Il for linux-arm-kernel@lists.infradead.org; Thu, 27 Jan 2022 19:25:00 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E67E0113E; Thu, 27 Jan 2022 11:24:56 -0800 (PST) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.196.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id ED4243F7D7; Thu, 27 Jan 2022 11:24:53 -0800 (PST) From: Valentin Schneider To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rt-users@vger.kernel.org Cc: Sebastian Andrzej Siewior , Catalin Marinas , Will Deacon , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Steven Rostedt , Daniel Bristot de Oliveira , "Paul E. McKenney" , Frederic Weisbecker , Josh Triplett , Mathieu Desnoyers , Davidlohr Bueso , Lai Jiangshan , Joel Fernandes , Anshuman Khandual , Vincenzo Frascino , Steven Price , Ard Biesheuvel , Boqun Feng , Mike Galbraith Subject: [PATCH v4] arm64: mm: Make arch_faults_on_old_pte() check for migratability Date: Thu, 27 Jan 2022 19:24:37 +0000 Message-Id: <20220127192437.1192957-1-valentin.schneider@arm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220127_112458_684895_0F365C08 X-CRM114-Status: GOOD ( 10.56 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org arch_faults_on_old_pte() relies on the calling context being non-preemptible. CONFIG_PREEMPT_RT turns the PTE lock into a sleepable spinlock, which doesn't disable preemption once acquired, triggering the warning in arch_faults_on_old_pte(). It does however disable migration, ensuring the task remains on the same CPU during the entirety of the critical section, making the read of cpu_has_hw_af() safe and stable. Make arch_faults_on_old_pte() check cant_migrate() instead of preemptible(). Suggested-by: Sebastian Andrzej Siewior Signed-off-by: Valentin Schneider Link: https://lore.kernel.org/r/20210811201354.1976839-5-valentin.schneider@arm.com --- v3 -> v4: Dropped migratable(), reuse cant_migrate() (Sebastian) --- arch/arm64/include/asm/pgtable.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index c4ba047a82d2..3caf6346ea95 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1001,7 +1001,8 @@ static inline void update_mmu_cache(struct vm_area_struct *vma, */ static inline bool arch_faults_on_old_pte(void) { - WARN_ON(preemptible()); + /* The register read below requires a stable CPU to make any sense */ + cant_migrate(); return !cpu_has_hw_af(); } -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel