Re: [PATCH v13 09/13] iommu/sva: Refactoring iommu_sva_bind/unbind_device()

From: Baolu Lu <baolu.lu@linux.intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
	Christoph Hellwig <hch@infradead.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Kevin Tian <kevin.tian@intel.com>,
	Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>, Vinod Koul <vkoul@kernel.org>,
	Eric Auger <eric.auger@redhat.com>, Liu Yi L <yi.l.liu@intel.com>,
	Jacob jun Pan <jacob.jun.pan@intel.com>,
	Zhangfei Gao <zhangfei.gao@linaro.org>,
	Zhu Tony <tony.zhu@intel.com>,
	iommu@lists.linux.dev, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v13 09/13] iommu/sva: Refactoring iommu_sva_bind/unbind_device()
Date: Fri, 9 Sep 2022 09:54:07 +0800	[thread overview]
Message-ID: <a4402d04-0920-59ff-5dd3-a374c84d64b0@linux.intel.com> (raw)
In-Reply-To: <YxobR/brG9VlxPvX@nvidia.com>

On 2022/9/9 0:41, Jason Gunthorpe wrote:
> On Thu, Sep 08, 2022 at 05:25:32PM +0100, Jean-Philippe Brucker wrote:
>> On Wed, Sep 07, 2022 at 02:33:11PM -0300, Jason Gunthorpe wrote:
>>> On Wed, Sep 07, 2022 at 10:54:54AM +0100, Jean-Philippe Brucker wrote:
>>>
>>>> Is iommu_domain still going to represent both a device context (whole
>>>> PASID table) and individual address spaces, or are you planning to move
>>>> away from that?  What happens when a driver does:
>>>>
>>>>    d1 = iommu_domain_alloc()
>>>>    iommu_attach_device(d1)
>>>>    d2 = iommu_sva_bind_device()
>>>>    iommu_detach_device(d1)
>>>>
>>>> Does detach
>>>> (a) only disable the non-PASID address space?
>>>> (b) disable everything?
>>>> (c) fail because the driver didn't unbind first?
>>> I think it must be (a), considering how everything is defined and the
>>> needs for vIOMMU emulation.
>> Yes (a) is probably better. The SMMU driver currently implements (c) to
>> ensure that you can't switch device driver without unbinding everything
>> first, and we should keep that check somewhere
> Yes, the owner stuff is a logical place to put that, when ownership
> is all released the PASID table of the group must be empty. Lu?

I agree. The ownership is about the whole device (more precisely,
group), including the RID and PASIDs. When the ownership is converted,
the pasid array must be empty. I will add code in this series to enforce
this. Thanks for pointing out this.

Best regards,
baolu