From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) (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 6A2D4EB8 for ; Tue, 23 Aug 2022 07:30:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1661239851; x=1692775851; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=j51hMQhIOMj+pWMUO1f6irDGuNzX4i/XllUj8uvQjxw=; b=J+aaFbYUgyZk3SN304mEVzUBpKbBJx03QDJhWlFhZ+8PtUOsO10YD6Q+ Clj8F9f+5i8SDEFz5XAin1JQDHFhj5YTh96nlkrCJzSpcn7HyEADG4BB1 abupMYzc2pQD10CWtFyOWg7YUh1LRyehgMEdU1n4j/RavpWvXMLBTyF0f fuFuRvs++aNdrNQQWicqzGsWnMcPvXQ164qR7PN9bCKqVyAAaklkUD9+T ysa6rrtzTRntWXJY1O/zaCGHaLkKqLZBJdhJqGzW+372pg+7lNJpgQKUQ kSW61gut10lC8F+cOpX0zajNNR4T3JjxXaNRFZ3goqmHxIBte4TAT38ab Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10447"; a="293614300" X-IronPort-AV: E=Sophos;i="5.93,256,1654585200"; d="scan'208";a="293614300" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Aug 2022 00:30:31 -0700 X-IronPort-AV: E=Sophos;i="5.93,256,1654585200"; d="scan'208";a="642344795" Received: from xujinlon-mobl.ccr.corp.intel.com (HELO [10.254.211.102]) ([10.254.211.102]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Aug 2022 00:30:23 -0700 Message-ID: Date: Tue, 23 Aug 2022 15:30:21 +0800 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Cc: baolu.lu@linux.intel.com, Joerg Roedel , Christoph Hellwig , Bjorn Helgaas , Kevin Tian , Ashok Raj , Will Deacon , Robin Murphy , Jean-Philippe Brucker , Dave Jiang , Vinod Koul , Eric Auger , Liu Yi L , Jacob jun Pan , Zhangfei Gao , Zhu Tony , iommu@lists.linux.dev, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Jean-Philippe Brucker Subject: Re: [PATCH v11 05/13] iommu: Add attach/detach_dev_pasid iommu interface Content-Language: en-US To: Jason Gunthorpe References: <20220817012024.3251276-1-baolu.lu@linux.intel.com> <20220817012024.3251276-6-baolu.lu@linux.intel.com> From: Baolu Lu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2022/8/18 21:33, Jason Gunthorpe wrote: > On Wed, Aug 17, 2022 at 09:20:16AM +0800, Lu Baolu wrote: > >> +static int __iommu_set_group_pasid(struct iommu_domain *domain, >> + struct iommu_group *group, ioasid_t pasid) >> +{ >> + struct iommu_domain *ops_domain; >> + struct group_device *device; >> + int ret = 0; >> + >> + if (domain == group->blocking_domain) >> + ops_domain = xa_load(&group->pasid_array, pasid); >> + else >> + ops_domain = domain; > > This seems weird, why isn't this just always > > domain->ops->set_dev_pasid()? Sure. I will fix this in the next version. > >> + if (curr) { >> + ret = xa_err(curr) ? : -EBUSY; >> + goto out_unlock; >> + } >> + >> + ret = __iommu_set_group_pasid(domain, group, pasid); >> + if (ret) { >> + __iommu_set_group_pasid(group->blocking_domain, group, pasid); >> + xa_erase(&group->pasid_array, pasid); > > I was looking at this trying to figure out why we are having > attach/detach semantics vs set and this error handling seems to be the > reason > > Lets add a comment because it is subtle thing: > > Setting a PASID to a blocking domain cannot fail, so we can always > safely error unwind a failure to attach a domain back to the original > group configuration of the PASID being unused. Updated. > >> +/* >> + * iommu_detach_device_pasid() - Detach the domain from pasid of device >> + * @domain: the iommu domain. >> + * @dev: the attached device. >> + * @pasid: the pasid of the device. >> + * >> + * The @domain must have been attached to @pasid of the @dev with >> + * iommu_attach_device_pasid(). >> + */ >> +void iommu_detach_device_pasid(struct iommu_domain *domain, struct device *dev, >> + ioasid_t pasid) > > Don't pass domain here? It is checked in the function to make sure that the detached domain is the same one as the previous attached one. > >> +/* >> + * iommu_get_domain_for_dev_pasid() - Retrieve domain for @pasid of @dev >> + * @dev: the queried device >> + * @pasid: the pasid of the device >> + * >> + * This is a variant of iommu_get_domain_for_dev(). It returns the existing >> + * domain attached to pasid of a device. It's only for internal use of the >> + * IOMMU subsystem. The caller must take care to avoid any possible >> + * use-after-free case. > > How exactly does the caller manage that? "... the returned domain pointer could only be used before detaching from the device PASID." > >> + * >> + * Return: attached domain on success, NULL otherwise. >> + */ >> +struct iommu_domain * >> +iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid) >> +{ >> + struct iommu_domain *domain; >> + struct iommu_group *group; >> + >> + if (!pasid_valid(pasid)) >> + return NULL; > > Why bother? If the pasid is not valid then it definitely won't be in the xarray. Removed. > But otherwise this overall thing seems fine to me Thank you! Best regards, baolu