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 92C79C43334 for ; Wed, 6 Jul 2022 01:39:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229482AbiGFBjq (ORCPT ); Tue, 5 Jul 2022 21:39:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39716 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229453AbiGFBjp (ORCPT ); Tue, 5 Jul 2022 21:39:45 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EB4D186F8; Tue, 5 Jul 2022 18:39:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1657071585; x=1688607585; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=fJxV3N/r8RRwYOaYdoJK639dTHZ5BBDCFg7PkYP7v3w=; b=cTYBlLL6lIry7NYEoVTGdTxGiUOBL1GQ//oKN4e7iIHFjjDNSgVu8ZYT HzRGPhvKPoX6EJWwuVqTmlZnScUjXWH7nQxVLuMqNmmZWQKKbtxpar79/ yQ5X6zpXcV05TeXmf2gzlyqBiNJeTHxYnLtOPd6QEiWUkiMdZakXFOW/u D5WkXg3QtC8BkN7b7xoH+t3ZAfPUjO1AI+osBcUy6rFUIUPRm3Sq7U8GH zJwA0PSsck7KMvQaLBMWvEzL07fsvuPsleJTpcoNdsB8n1HwvoOL7OjO2 p9eK+zHSAFVihHBsWfjfdI6IvJzl/PhOVOC0d0HQKBXwbJPydkdDmwbk5 Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10399"; a="264032764" X-IronPort-AV: E=Sophos;i="5.92,248,1650956400"; d="scan'208";a="264032764" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Jul 2022 18:39:45 -0700 X-IronPort-AV: E=Sophos;i="5.92,248,1650956400"; d="scan'208";a="650429732" Received: from zhuoliu-mobl1.ccr.corp.intel.com (HELO [10.249.174.206]) ([10.249.174.206]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Jul 2022 18:39:42 -0700 Message-ID: <032937a0-ffef-221c-4faf-4680fa09b2af@linux.intel.com> Date: Wed, 6 Jul 2022 09:39:40 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Cc: baolu.lu@linux.intel.com, will@kernel.org, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, suravee.suthikulpanit@amd.com, vasant.hegde@amd.com, mjrosato@linux.ibm.com, gerald.schaefer@linux.ibm.com, schnelle@linux.ibm.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 01/15] iommu/vt-d: Handle race between registration and device probe Content-Language: en-US To: Robin Murphy , joro@8bytes.org References: <894db0ccae854b35c73814485569b634237b5538.1657034828.git.robin.murphy@arm.com> From: Baolu Lu In-Reply-To: <894db0ccae854b35c73814485569b634237b5538.1657034828.git.robin.murphy@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 2022/7/6 01:08, Robin Murphy wrote: > Currently we rely on registering all our instances before initially > allowing any .probe_device calls via bus_set_iommu(). In preparation for > phasing out the latter, make sure we won't inadvertently return success > for a device associated with a known but not yet registered instance, > otherwise we'll run straight into iommu_group_get_for_dev() trying to > use NULL ops. > > That also highlights an issue with intel_iommu_get_resv_regions() taking > dmar_global_lock from within a section where intel_iommu_init() already > holds it, which already exists via probe_acpi_namespace_devices() when > an ANDD device is probed, but gets more obvious with the upcoming change > to iommu_device_register(). Since they are both read locks it manages > not to deadlock in practice, so I'm leaving it here for someone with > more confidence to tackle a larger rework of the locking. Thanks for highlighting this. I will look into it later. Best regards, baolu > > Signed-off-by: Robin Murphy > --- > > v3: New > > drivers/iommu/intel/iommu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c > index 44016594831d..3e02c08802a0 100644 > --- a/drivers/iommu/intel/iommu.c > +++ b/drivers/iommu/intel/iommu.c > @@ -4600,7 +4600,7 @@ static struct iommu_device *intel_iommu_probe_device(struct device *dev) > u8 bus, devfn; > > iommu = device_to_iommu(dev, &bus, &devfn); > - if (!iommu) > + if (!iommu || !iommu->iommu.ops) > return ERR_PTR(-ENODEV); > > info = kzalloc(sizeof(*info), GFP_KERNEL);