From nobody Mon Feb 9 10:24:38 2026 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 A6AC1C761A6 for ; Wed, 29 Mar 2023 13:47:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229945AbjC2NrP (ORCPT ); Wed, 29 Mar 2023 09:47:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229687AbjC2NrM (ORCPT ); Wed, 29 Mar 2023 09:47:12 -0400 Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 76AEB12B for ; Wed, 29 Mar 2023 06:47:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1680097631; x=1711633631; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=yixgjd44s0XfELjSEuxjT4sSEHUeg+Rlr7hga8v5ee0=; b=abFRDO2XZnPYAt1tuzJGPdMAZg1WKXsrTwhlMT0RCSyy8kqHh31E16P9 Bbveg2dqQB7Wi4PIArCJeZc4NAapojl+6Q/TOG3DFSGoqjL5ScTlPiji4 GG5FATc+FlPfMzzM+f80nHsOCB4txoXuMM1gj7owhNvAfetW88taJglh3 sGTO7kQ5qBjmdDZXxlkDJFy3nj2oW2U3S6jXTQsR5EfmN1K2gysRETNEX UbNn+R+IZRoKnHYsSyepWc56oXUfqz0UPIYzaowaBZslXjophDGI0F+si 7OPzkNz4awLxXMUAjGTNvohDyZ2AVoYPeA9cAvqeesbQM5VYakSqCux9F w==; X-IronPort-AV: E=McAfee;i="6600,9927,10664"; a="403506231" X-IronPort-AV: E=Sophos;i="5.98,300,1673942400"; d="scan'208";a="403506231" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Mar 2023 06:47:07 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10664"; a="677783357" X-IronPort-AV: E=Sophos;i="5.98,300,1673942400"; d="scan'208";a="677783357" Received: from allen-box.sh.intel.com ([10.239.159.48]) by orsmga007.jf.intel.com with ESMTP; 29 Mar 2023 06:47:05 -0700 From: Lu Baolu To: Joerg Roedel Cc: Kan Liang , Lu Baolu , iommu@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH 1/3] iommu/vt-d: Remove unnecessary locking in intel_irq_remapping_alloc() Date: Wed, 29 Mar 2023 21:47:19 +0800 Message-Id: <20230329134721.469447-2-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230329134721.469447-1-baolu.lu@linux.intel.com> References: <20230329134721.469447-1-baolu.lu@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D 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") Reviewed-by: Jacob Pan Tested-by: Jason Gunthorpe Signed-off-by: Lu Baolu Link: https://lore.kernel.org/r/20230314051836.23817-1-baolu.lu@linux.intel= .com --- 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; =20 - down_read(&dmar_global_lock); for (i =3D 0; i < MAX_IO_APICS; i++) { if (ir_ioapic[i].iommu && ir_ioapic[i].id =3D=3D apic) { sid =3D (ir_ioapic[i].bus << 8) | ir_ioapic[i].devfn; break; } } - up_read(&dmar_global_lock); =20 if (sid =3D=3D 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; =20 - down_read(&dmar_global_lock); for (i =3D 0; i < MAX_HPET_TBS; i++) { if (ir_hpet[i].iommu && ir_hpet[i].id =3D=3D id) { sid =3D (ir_hpet[i].bus << 8) | ir_hpet[i].devfn; break; } } - up_read(&dmar_global_lock); =20 if (sid =3D=3D 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_domai= n *domain, if (!data) goto out_free_parent; =20 - down_read(&dmar_global_lock); index =3D 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); --=20 2.34.1