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 916F7C43217 for ; Tue, 7 Dec 2021 02:07:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238941AbhLGCLD (ORCPT ); Mon, 6 Dec 2021 21:11:03 -0500 Received: from mga12.intel.com ([192.55.52.136]:4195 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231245AbhLGCLA (ORCPT ); Mon, 6 Dec 2021 21:11:00 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10190"; a="217487427" X-IronPort-AV: E=Sophos;i="5.87,293,1631602800"; d="scan'208";a="217487427" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Dec 2021 18:07:30 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.87,293,1631602800"; d="scan'208";a="515046131" Received: from allen-box.sh.intel.com (HELO [10.239.159.118]) ([10.239.159.118]) by orsmga008.jf.intel.com with ESMTP; 06 Dec 2021 18:07:23 -0800 Cc: baolu.lu@linux.intel.com, Greg Kroah-Hartman , Joerg Roedel , Alex Williamson , Bjorn Helgaas , Jason Gunthorpe , Kevin Tian , Ashok Raj , Will Deacon , Robin Murphy , 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 v3 01/18] iommu: Add device dma ownership set/release interfaces To: Christoph Hellwig References: <20211206015903.88687-1-baolu.lu@linux.intel.com> <20211206015903.88687-2-baolu.lu@linux.intel.com> From: Lu Baolu Message-ID: <2872aa9f-c325-ca28-fb64-f86857ad3e91@linux.intel.com> Date: Tue, 7 Dec 2021 10:07:16 +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: 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 12/6/21 10:42 PM, Christoph Hellwig wrote: > On Mon, Dec 06, 2021 at 09:58:46AM +0800, Lu Baolu wrote: >> >From the perspective of who is initiating the device to do DMA, device >> DMA could be divided into the following types: >> >> DMA_OWNER_DMA_API: Device DMAs are initiated by a kernel driver >> through the kernel DMA API. >> DMA_OWNER_PRIVATE_DOMAIN: Device DMAs are initiated by a kernel >> driver with its own PRIVATE domain. >> DMA_OWNER_PRIVATE_DOMAIN_USER: Device DMAs are initiated by >> userspace. >> >> Different DMA ownerships are exclusive for all devices in the same iommu >> group as an iommu group is the smallest granularity of device isolation >> and protection that the IOMMU subsystem can guarantee. This extends the >> iommu core to enforce this exclusion. >> >> Basically two new interfaces are provided: >> >> int iommu_device_set_dma_owner(struct device *dev, >> enum iommu_dma_owner type, void *owner_cookie); >> void iommu_device_release_dma_owner(struct device *dev, >> enum iommu_dma_owner type); >> >> Although above interfaces are per-device, DMA owner is tracked per group >> under the hood. An iommu group cannot have different dma ownership set >> at the same time. Violation of this assumption fails >> iommu_device_set_dma_owner(). >> >> Kernel driver which does DMA have DMA_OWNER_DMA_API automatically set/ >> released in the driver binding/unbinding process (see next patch). >> >> Kernel driver which doesn't do DMA could avoid setting the owner type. >> Device bound to such driver is considered same as a driver-less device >> which is compatible to all owner types. >> >> Userspace driver framework (e.g. vfio) should set >> DMA_OWNER_PRIVATE_DOMAIN_USER for a device before the userspace is allowed >> to access it, plus a owner cookie pointer to mark the user identity so a >> single group cannot be operated by multiple users simultaneously. Vice >> versa, the owner type should be released after the user access permission >> is withdrawn. >> >> Signed-off-by: Jason Gunthorpe >> Signed-off-by: Kevin Tian >> Signed-off-by: Lu Baolu >> --- >> include/linux/iommu.h | 36 +++++++++++++++++ >> drivers/iommu/iommu.c | 93 +++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 129 insertions(+) >> >> diff --git a/include/linux/iommu.h b/include/linux/iommu.h >> index d2f3435e7d17..24676b498f38 100644 >> --- a/include/linux/iommu.h >> +++ b/include/linux/iommu.h >> @@ -162,6 +162,23 @@ enum iommu_dev_features { >> IOMMU_DEV_FEAT_IOPF, >> }; >> >> +/** >> + * enum iommu_dma_owner - IOMMU DMA ownership >> + * @DMA_OWNER_NONE: No DMA ownership. >> + * @DMA_OWNER_DMA_API: Device DMAs are initiated by a kernel driver through >> + * the kernel DMA API. >> + * @DMA_OWNER_PRIVATE_DOMAIN: Device DMAs are initiated by a kernel driver >> + * which provides an UNMANAGED domain. >> + * @DMA_OWNER_PRIVATE_DOMAIN_USER: Device DMAs are initiated by userspace, >> + * kernel ensures that DMAs never go to kernel memory. >> + */ >> +enum iommu_dma_owner { >> + DMA_OWNER_NONE, >> + DMA_OWNER_DMA_API, >> + DMA_OWNER_PRIVATE_DOMAIN, >> + DMA_OWNER_PRIVATE_DOMAIN_USER, >> +}; >> + >> #define IOMMU_PASID_INVALID (-1U) >> >> #ifdef CONFIG_IOMMU_API >> @@ -681,6 +698,10 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, >> void iommu_sva_unbind_device(struct iommu_sva *handle); >> u32 iommu_sva_get_pasid(struct iommu_sva *handle); >> >> +int iommu_device_set_dma_owner(struct device *dev, enum iommu_dma_owner owner, >> + void *owner_cookie); >> +void iommu_device_release_dma_owner(struct device *dev, enum iommu_dma_owner owner); >> + >> #else /* CONFIG_IOMMU_API */ >> >> struct iommu_ops {}; >> @@ -1081,6 +1102,21 @@ static inline struct iommu_fwspec *dev_iommu_fwspec_get(struct device *dev) >> { >> return NULL; >> } >> + >> +static inline int iommu_device_set_dma_owner(struct device *dev, >> + enum iommu_dma_owner owner, >> + void *owner_cookie) >> +{ >> + if (owner != DMA_OWNER_DMA_API) >> + return -EINVAL; >> + >> + return 0; >> +} >> + >> +static inline void iommu_device_release_dma_owner(struct device *dev, >> + enum iommu_dma_owner owner) >> +{ >> +} >> #endif /* CONFIG_IOMMU_API */ >> >> /** >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >> index 8b86406b7162..1de520a07518 100644 >> --- a/drivers/iommu/iommu.c >> +++ b/drivers/iommu/iommu.c >> @@ -48,6 +48,9 @@ struct iommu_group { >> struct iommu_domain *default_domain; >> struct iommu_domain *domain; >> struct list_head entry; >> + enum iommu_dma_owner dma_owner; >> + refcount_t owner_cnt; > > owner_cnt is only manipulated under group->mutex, not need for a > refcount_t here, a plain unsigned int while do it and will also > simplify a fair bit of code as it avoid the need for atomic add/sub > and test operations. Fair enough. > >> +static int __iommu_group_set_dma_owner(struct iommu_group *group, >> + enum iommu_dma_owner owner, >> + void *owner_cookie) >> +{ > > As pointed out last time, please move the group->mutex locking into > this helper, which makes it identical to the later added public > function. I didn't mean to ignore your comment. :-) As I replied, by placing the lock out of the function, the helper could easily handle the error paths (return directly without something like "goto out_unlock"). As the implementation of iommu_group_set_dma_owner() has been greatly simplified, I agree with you now, we should move the group->mutex locking into the helper and make it identical to the latter public interface. I will work towards this. > >> +static void __iommu_group_release_dma_owner(struct iommu_group *group, >> + enum iommu_dma_owner owner) >> +{ > > Same here. > Ditto. Best regards, baolu