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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA70BC33CB1 for ; Tue, 14 Jan 2020 15:25:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9BFDF207E0 for ; Tue, 14 Jan 2020 15:25:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579015547; bh=lCzT2r10t8tKjNMq10HvvXZufirJmV3nQEiebEYP3gc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=LL5Hi3nvuuARj+nqlCUw9PJgSCxsfZ18oHUdYfl+hygcTSk1D4TiFlp+ti+GVDfLd ab2VM4FY/WgP7P+9ZdjK8hquH5uMX0zuAGEXYb3z2Gk1VOzHtunD4Sl/tWMtC/LMl8 mPxbcBiqszFwGOZ0vhF/dta6q5X3RaaQAsBAQqRA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728656AbgANPZr (ORCPT ); Tue, 14 Jan 2020 10:25:47 -0500 Received: from mail.kernel.org ([198.145.29.99]:43950 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725904AbgANPZq (ORCPT ); Tue, 14 Jan 2020 10:25:46 -0500 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 945E02072B; Tue, 14 Jan 2020 15:25:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579015545; bh=lCzT2r10t8tKjNMq10HvvXZufirJmV3nQEiebEYP3gc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RkN7x9BHeMRrLPT+H/Vs2eAvyxwdMCtxWZmirmotOXrXKM50Xkbz2VUrqG8FcVImK P8szE3NrMlFvQuC5m4VfQX6pJmIKvCFzay0rFPkLwzHVZLgYMzftKk7hUjTc4jYYru GRgHe2lPXAh9kwyaBFQssQ72gTeD94bIFnjasRYo= Date: Tue, 14 Jan 2020 15:25:39 +0000 From: Will Deacon To: Jean-Philippe Brucker , robin.murphy@arm.com Cc: linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org, devicetree@vger.kernel.org, iommu@lists.linux-foundation.org, joro@8bytes.org, robh+dt@kernel.org, mark.rutland@arm.com, lorenzo.pieralisi@arm.com, guohanjun@huawei.com, sudeep.holla@arm.com, rjw@rjwysocki.net, lenb@kernel.org, robin.murphy@arm.com, bhelgaas@google.com, eric.auger@redhat.com, jonathan.cameron@huawei.com, zhangfei.gao@linaro.org Subject: Re: [PATCH v4 11/13] iommu/arm-smmu-v3: Improve add_device() error handling Message-ID: <20200114152538.GB2579@willie-the-truck> References: <20191219163033.2608177-1-jean-philippe@linaro.org> <20191219163033.2608177-12-jean-philippe@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191219163033.2608177-12-jean-philippe@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Dec 19, 2019 at 05:30:31PM +0100, Jean-Philippe Brucker wrote: > Let add_device() clean up after itself. The iommu_bus_init() function > does call remove_device() on error, but other sites (e.g. of_iommu) do > not. > > Don't free level-2 stream tables because we'd have to track if we > allocated each of them or if they are used by other endpoints. It's not > worth the hassle since they are managed resources. > > Reviewed-by: Eric Auger > Reviewed-by: Jonathan Cameron > Signed-off-by: Jean-Philippe Brucker > --- > drivers/iommu/arm-smmu-v3.c | 28 +++++++++++++++++++++------- > 1 file changed, 21 insertions(+), 7 deletions(-) I think this is alright, with one caveat relating to: /* * We _can_ actually withstand dodgy bus code re-calling add_device() * without an intervening remove_device()/of_xlate() sequence, but * we're not going to do so quietly... */ if (WARN_ON_ONCE(fwspec->iommu_priv)) { master = fwspec->iommu_priv; smmu = master->smmu; } ... which may be on shakey ground if the subsequent add_device() call can fail and free stuff that the first one allocated. At least, I don't know what we're trying to support with this, so it's hard to tell whether or not it still works as intended after your change. How is this supposed to work? I don't recall ever seeing that WARN fire, so can we just remove this and bail instead? Robin? Something like below before your changes... Will --->8 diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index effe72eb89e7..6ae3df2f3495 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -2534,28 +2534,23 @@ static int arm_smmu_add_device(struct device *dev) if (!fwspec || fwspec->ops != &arm_smmu_ops) return -ENODEV; - /* - * We _can_ actually withstand dodgy bus code re-calling add_device() - * without an intervening remove_device()/of_xlate() sequence, but - * we're not going to do so quietly... - */ - if (WARN_ON_ONCE(fwspec->iommu_priv)) { - master = fwspec->iommu_priv; - smmu = master->smmu; - } else { - smmu = arm_smmu_get_by_fwnode(fwspec->iommu_fwnode); - if (!smmu) - return -ENODEV; - master = kzalloc(sizeof(*master), GFP_KERNEL); - if (!master) - return -ENOMEM; - master->dev = dev; - master->smmu = smmu; - master->sids = fwspec->ids; - master->num_sids = fwspec->num_ids; - fwspec->iommu_priv = master; - } + if (WARN_ON_ONCE(fwspec->iommu_priv)) + return -EBUSY; + + smmu = arm_smmu_get_by_fwnode(fwspec->iommu_fwnode); + if (!smmu) + return -ENODEV; + + master = kzalloc(sizeof(*master), GFP_KERNEL); + if (!master) + return -ENOMEM; + + master->dev = dev; + master->smmu = smmu; + master->sids = fwspec->ids; + master->num_sids = fwspec->num_ids; + fwspec->iommu_priv = master; /* Check the SIDs are in range of the SMMU and our stream table */ for (i = 0; i < master->num_sids; i++) {