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 2729FC433F5 for ; Wed, 22 Dec 2021 04:22:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242349AbhLVEWn (ORCPT ); Tue, 21 Dec 2021 23:22:43 -0500 Received: from mga11.intel.com ([192.55.52.93]:35737 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232658AbhLVEWl (ORCPT ); Tue, 21 Dec 2021 23:22:41 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1640146961; x=1671682961; h=cc:subject:to:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=Cyl3EnNuBUB+YdjCSptEMAFJt9rmebRqepgSebgdx4Q=; b=LtVgxlrocd0EMvyq+oCmRBTDZTP9+aOyjHav4HhYp3VnPIs8MiKtGJWp rLFxhAqqfnpuvnWFAYqn3Z3aR+UXC7mXeQpbS4iQWtVrbk/iEXqMWAmKS DFm0diAF5oj9C0rXxpq1vMZnttTAj+jRQDcwSU90TAIfYuMI3qPwO9oI4 PMZfhGTlYIfCjSBGn1ZkgfgW+cv+EOa7V+BAUGVmayd1s4feRarkY5Ej2 JpEv8yO7g1g2625OT6uGUaAtCo3EZLfS4dCN0Uho5KYpXCY10PcKzm0JF H46gsMNRgTBjTiHPIstzbzWn3dlLeNejKrW4L70zNa97X1e1VJqEV8uMW A==; X-IronPort-AV: E=McAfee;i="6200,9189,10205"; a="238078551" X-IronPort-AV: E=Sophos;i="5.88,225,1635231600"; d="scan'208";a="238078551" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Dec 2021 20:22:41 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,225,1635231600"; d="scan'208";a="664154927" Received: from allen-box.sh.intel.com (HELO [10.239.159.118]) ([10.239.159.118]) by fmsmga001.fm.intel.com with ESMTP; 21 Dec 2021 20:22:34 -0800 Cc: baolu.lu@linux.intel.com, Greg Kroah-Hartman , Joerg Roedel , Alex Williamson , Bjorn Helgaas , Christoph Hellwig , Kevin Tian , Ashok Raj , Will Deacon , Dan Williams , rafael@kernel.org, Diana Craciun , Cornelia Huck , Eric Auger , Liu Yi L , Jacob jun Pan , Chaitanya Kulkarni , Stuart Yoder , Laurentiu Tudor , Thierry Reding , David Airlie , Daniel Vetter , Jonathan Hunter , Li Yang , Dmitry Osipenko , iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 07/13] iommu: Add iommu_at[de]tach_device_shared() for multi-device groups To: Jason Gunthorpe , Robin Murphy References: <20211217063708.1740334-1-baolu.lu@linux.intel.com> <20211217063708.1740334-8-baolu.lu@linux.intel.com> <20211221184609.GF1432915@nvidia.com> From: Lu Baolu Message-ID: Date: Wed, 22 Dec 2021 12:22:11 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211221184609.GF1432915@nvidia.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/22/21 2:46 AM, Jason Gunthorpe wrote: >> It's worth taking a step back and realising that overall, this is really >> just a more generalised and finer-grained extension of what 426a273834ea >> already did for non-group-aware code, so it makes little sense*not* to >> integrate it into the existing interfaces. > This is taking 426a to it's logical conclusion and*removing* the > group API from the drivers entirely. This is desirable because drivers > cannot do anything sane with the group. > > The drivers have struct devices, and so we provide APIs that work in > terms of struct devices to cover both driver use cases today, and do > so more safely than what is already implemented. > > Do not mix up VFIO with the driver interface, these are different > things. It is better VFIO stay on its own and not complicate the > driver world. Per Joerg's previous comments: https://lore.kernel.org/linux-iommu/20211119150612.jhsvsbzisvux2lga@8bytes.org/ The commit 426a273834ea came only in order to disallow attaching a single device within a group to a different iommu_domain. So it's reasonable to improve the existing iommu_attach/detach_device() to cover all cases. How about below code? Did I miss anything? int iommu_attach_device(struct iommu_domain *domain, struct device *dev) { struct iommu_group *group; int ret = 0; group = iommu_group_get(dev); if (!group) return -ENODEV; mutex_lock(&group->mutex); if (group->attach_cnt) { if (group->domain != domain) { ret = -EBUSY; goto unlock_out; } } else { ret = __iommu_attach_group(domain, group); if (ret) goto unlock_out; } group->attach_cnt++; unlock_out: mutex_unlock(&group->mutex); iommu_group_put(group); return ret; } EXPORT_SYMBOL_GPL(iommu_attach_device); void iommu_detach_device_shared(struct iommu_domain *domain, struct device *dev) { struct iommu_group *group; group = iommu_group_get(dev); if (WARN_ON(!group)) return; mutex_lock(&group->mutex); if (WARN_ON(!group->attach_cnt || group->domain != domain) goto unlock_out; if (--group->attach_cnt == 0) __iommu_detach_group(domain, group); unlock_out: mutex_unlock(&group->mutex); iommu_group_put(group); } EXPORT_SYMBOL_GPL(iommu_detach_device); Best regards, baolu