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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0656C74A44 for ; Tue, 14 Mar 2023 05:19:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229735AbjCNFTr (ORCPT ); Tue, 14 Mar 2023 01:19:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229528AbjCNFTq (ORCPT ); Tue, 14 Mar 2023 01:19:46 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3132951FBB for ; Mon, 13 Mar 2023 22:19:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1678771185; x=1710307185; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=AgQ9bSzSPzcGMLNoWPFkB0EICC/cZjX30lB9FzLG2Pc=; b=FqS0PNy2gViVtnQPiqw+UsQ7vsbqyu3b0bnUW+VrkfkdtVbNenyMjHOA cKKf2yQayvHDdj3gLJmXU1W3uZuPmM6zxj8jUK6cvUY6q7Rl23BApJ590 UcihPl20Y1elye5ci1Wxi3NKPjVeM8y/lnzkK23Qm/Cl3++uwI7HhMAwf +4e3vUXPeCl1IlcDUB65AqAdTpeO7gi9830E341x1lgBHqpd8ygk5YtUs 3r1+uMJdhpkLc0ZkQ5L+rIE8lorVdhtAKWAwFMGxTFmPvOilEGsFRXOhs AzNHT+AsP8JfNq+4xgCvIwKYUZDCK7Rb6gN8meAzAI4Sxcg4JZVyVJwhn A==; X-IronPort-AV: E=McAfee;i="6500,9779,10648"; a="402205411" X-IronPort-AV: E=Sophos;i="5.98,259,1673942400"; d="scan'208";a="402205411" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Mar 2023 22:19:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10648"; a="709139698" X-IronPort-AV: E=Sophos;i="5.98,259,1673942400"; d="scan'208";a="709139698" Received: from allen-box.sh.intel.com ([10.239.159.48]) by orsmga008.jf.intel.com with ESMTP; 13 Mar 2023 22:19:42 -0700 From: Lu Baolu To: iommu@lists.linux.dev Cc: Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , linux-kernel@vger.kernel.org, Lu Baolu Subject: [PATCH] iommu/vt-d: Remove unnecessary locking in intel_irq_remapping_alloc() Date: Tue, 14 Mar 2023 13:18:36 +0800 Message-Id: <20230314051836.23817-1-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The global rwsem dmar_global_lock was introduced by commit 3a5670e8ac932 ("iommu/vt-d: Introduce a rwsem to protect global data structures"). It is used to protect DMAR related global data from DMAR hotplug operations. Using dmar_global_lock in intel_irq_remapping_alloc() is unnecessary as the DMAR global data structures are not touched there. Remove it to avoid below lockdep warning. ====================================================== WARNING: possible circular locking dependency detected 6.3.0-rc2 #468 Not tainted ------------------------------------------------------ swapper/0/1 is trying to acquire lock: ff1db4cb40178698 (&domain->mutex){+.+.}-{3:3}, at: __irq_domain_alloc_irqs+0x3b/0xa0 but task is already holding lock: ffffffffa0c1cdf0 (dmar_global_lock){++++}-{3:3}, at: intel_iommu_init+0x58e/0x880 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (dmar_global_lock){++++}-{3:3}: lock_acquire+0xd6/0x320 down_read+0x42/0x180 intel_irq_remapping_alloc+0xad/0x750 mp_irqdomain_alloc+0xb8/0x2b0 irq_domain_alloc_irqs_locked+0x12f/0x2d0 __irq_domain_alloc_irqs+0x56/0xa0 alloc_isa_irq_from_domain.isra.7+0xa0/0xe0 mp_map_pin_to_irq+0x1dc/0x330 setup_IO_APIC+0x128/0x210 apic_intr_mode_init+0x67/0x110 x86_late_time_init+0x24/0x40 start_kernel+0x41e/0x7e0 secondary_startup_64_no_verify+0xe0/0xeb -> #0 (&domain->mutex){+.+.}-{3:3}: check_prevs_add+0x160/0xef0 __lock_acquire+0x147d/0x1950 lock_acquire+0xd6/0x320 __mutex_lock+0x9c/0xfc0 __irq_domain_alloc_irqs+0x3b/0xa0 dmar_alloc_hwirq+0x9e/0x120 iommu_pmu_register+0x11d/0x200 intel_iommu_init+0x5de/0x880 pci_iommu_init+0x12/0x40 do_one_initcall+0x65/0x350 kernel_init_freeable+0x3ca/0x610 kernel_init+0x1a/0x140 ret_from_fork+0x29/0x50 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(dmar_global_lock); lock(&domain->mutex); lock(dmar_global_lock); lock(&domain->mutex); *** DEADLOCK *** Fixes: 9dbb8e3452ab ("irqdomain: Switch to per-domain locking") Signed-off-by: Lu Baolu --- drivers/iommu/intel/irq_remapping.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c index 6d01fa078c36..df9e261af0b5 100644 --- a/drivers/iommu/intel/irq_remapping.c +++ b/drivers/iommu/intel/irq_remapping.c @@ -311,14 +311,12 @@ static int set_ioapic_sid(struct irte *irte, int apic) if (!irte) return -1; - down_read(&dmar_global_lock); for (i = 0; i < MAX_IO_APICS; i++) { if (ir_ioapic[i].iommu && ir_ioapic[i].id == apic) { sid = (ir_ioapic[i].bus << 8) | ir_ioapic[i].devfn; break; } } - up_read(&dmar_global_lock); if (sid == 0) { pr_warn("Failed to set source-id of IOAPIC (%d)\n", apic); @@ -338,14 +336,12 @@ static int set_hpet_sid(struct irte *irte, u8 id) if (!irte) return -1; - down_read(&dmar_global_lock); for (i = 0; i < MAX_HPET_TBS; i++) { if (ir_hpet[i].iommu && ir_hpet[i].id == id) { sid = (ir_hpet[i].bus << 8) | ir_hpet[i].devfn; break; } } - up_read(&dmar_global_lock); if (sid == 0) { pr_warn("Failed to set source-id of HPET block (%d)\n", id); @@ -1339,9 +1335,7 @@ static int intel_irq_remapping_alloc(struct irq_domain *domain, if (!data) goto out_free_parent; - down_read(&dmar_global_lock); index = alloc_irte(iommu, &data->irq_2_iommu, nr_irqs); - up_read(&dmar_global_lock); if (index < 0) { pr_warn("Failed to allocate IRTE\n"); kfree(data); -- 2.34.1