From nobody Wed Dec 17 02:56:15 2025 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 429AD25E836 for ; Fri, 28 Feb 2025 10:27:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.15 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740738435; cv=none; b=FtV0ojL+mYF06DEAUCf7Uub0VMpCV87T5LNc4Y1zJ379yBabbuxCM4uAArpA1fr0ACCmRC/uRtCub4rs5aXFi2HUoZS1Qs96lsJU42Lj6GgVetqEehgmjk8pqA3MNADxYxxfEQCzAGhNA0nVbN4SPlmEAIzLzh37Q8pz7R077Ck= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740738435; c=relaxed/simple; bh=xo5tsQZbpooLWFUPwrT+vqXnPUyi54lZIUsBGdgQg4o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Be7/uod/N16bzuIicofW57Moy/pxKM5nvEz4IEEUNpWkVgIH7Ly/FPuRrp9O9eZTtq5ATSTsH6fCj7Uh1+r+zegyugWzmRA19cId08OIZm5I2JjyZZNuwVq9JgWkJPoOt5vRm8Oz8DVKMr7PtcIOfFo2du3Wfl5C59t0uI7HdL8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Kk5l3bRe; arc=none smtp.client-ip=198.175.65.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Kk5l3bRe" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1740738434; x=1772274434; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=xo5tsQZbpooLWFUPwrT+vqXnPUyi54lZIUsBGdgQg4o=; b=Kk5l3bReGIvHhmvV4ENmIaLe1jcos/vYA95SKlYpNVwQlsl/EqpU3ezH /H93kjDjodrltSdPQJNJDJTxj8mYxDpECZ29PWjlk3i9qjodT6Sx9/sJ5 6I4G5rXagUsENzOVjc1TCHGSIzw+OI/Egu3TeoK5JQWTEBVAbs1gQ8CZk 7pv66qhhAvAtCFN5GFOehzJm2rsZEsOB+7yBomkLxluutpwiwTiZb/KRL OWm93gIhCka6CzDpy0bq7xxXSLESj+TExPPLs+aY/4goYXsQ7kHuPs8g+ 8tqU4+Q3tiUGX6DhMpwxHOEZB3L2NiPwN7yViCYYIWqKkSFQfr7yoLruk w==; X-CSE-ConnectionGUID: c8+U6wwvRryKOpw0QeAJ6w== X-CSE-MsgGUID: Kd9Hk1U5QOi+/oIFFBohyQ== X-IronPort-AV: E=McAfee;i="6700,10204,11358"; a="45313091" X-IronPort-AV: E=Sophos;i="6.13,322,1732608000"; d="scan'208";a="45313091" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Feb 2025 02:27:14 -0800 X-CSE-ConnectionGUID: pPE+RemPRYusGsftCxheIQ== X-CSE-MsgGUID: n2fAcSaTRvm/LMuDtOsouA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,322,1732608000"; d="scan'208";a="121909455" Received: from allen-box.sh.intel.com ([10.239.159.52]) by fmviesa005.fm.intel.com with ESMTP; 28 Feb 2025 02:27:13 -0800 From: Lu Baolu To: Joerg Roedel Cc: Jerry Snitselaar , iommu@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] iommu/vt-d: Fix suspicious RCU usage Date: Fri, 28 Feb 2025 18:27:26 +0800 Message-ID: <20250228102726.3429268-3-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250228102726.3429268-1-baolu.lu@linux.intel.com> References: <20250228102726.3429268-1-baolu.lu@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Commit ("iommu/vt-d: Allocate DMAR fault interrupts locally") moved the call to enable_drhd_fault_handling() to a code path that does not hold any lock while traversing the drhd list. Fix it by ensuring the dmar_global_lock lock is held when traversing the drhd list. Without this fix, the following warning is triggered: =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: suspicious RCU usage 6.14.0-rc3 #55 Not tainted ----------------------------- drivers/iommu/intel/dmar.c:2046 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active =3D 1, debug_locks =3D 1 2 locks held by cpuhp/1/23: #0: ffffffff84a67c50 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+= 0x87/0x2c0 #1: ffffffff84a6a380 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x= 87/0x2c0 stack backtrace: CPU: 1 UID: 0 PID: 23 Comm: cpuhp/1 Not tainted 6.14.0-rc3 #55 Call Trace: dump_stack_lvl+0xb7/0xd0 lockdep_rcu_suspicious+0x159/0x1f0 ? __pfx_enable_drhd_fault_handling+0x10/0x10 enable_drhd_fault_handling+0x151/0x180 cpuhp_invoke_callback+0x1df/0x990 cpuhp_thread_fun+0x1ea/0x2c0 smpboot_thread_fn+0x1f5/0x2e0 ? __pfx_smpboot_thread_fn+0x10/0x10 kthread+0x12a/0x2d0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x4a/0x60 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 Holding the lock in enable_drhd_fault_handling() triggers a lockdep splat about a possible deadlock between dmar_global_lock and cpu_hotplug_lock. This is avoided by not holding dmar_global_lock when calling iommu_device_register(), which initiates the device probe process. Fixes: d74169ceb0d2 ("iommu/vt-d: Allocate DMAR fault interrupts locally") Reported-and-tested-by: Ido Schimmel Closes: https://lore.kernel.org/linux-iommu/Zx9OwdLIc_VoQ0-a@shredder.mtl.c= om/ Tested-by: Breno Leitao Cc: stable@vger.kernel.org Signed-off-by: Lu Baolu Reviewed-by: Kevin Tian Link: https://lore.kernel.org/r/20250218022422.2315082-1-baolu.lu@linux.int= el.com --- drivers/iommu/intel/dmar.c | 1 + drivers/iommu/intel/iommu.c | 7 +++++++ 2 files changed, 8 insertions(+) diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c index 9f424acf474e..e540092d664d 100644 --- a/drivers/iommu/intel/dmar.c +++ b/drivers/iommu/intel/dmar.c @@ -2043,6 +2043,7 @@ int enable_drhd_fault_handling(unsigned int cpu) /* * Enable fault control interrupt. */ + guard(rwsem_read)(&dmar_global_lock); for_each_iommu(iommu, drhd) { u32 fault_status; int ret; diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 4d8d4593c9c8..bf1f0c814348 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -3146,7 +3146,14 @@ int __init intel_iommu_init(void) iommu_device_sysfs_add(&iommu->iommu, NULL, intel_iommu_groups, "%s", iommu->name); + /* + * The iommu device probe is protected by the iommu_probe_device_lock. + * Release the dmar_global_lock before entering the device probe path + * to avoid unnecessary lock order splat. + */ + up_read(&dmar_global_lock); iommu_device_register(&iommu->iommu, &intel_iommu_ops, NULL); + down_read(&dmar_global_lock); =20 iommu_pmu_register(iommu); } --=20 2.43.0