linux-kernel - Re: [PATCH v13 09/13] iommu/sva: Refactoring iommu_sva_bind/unbind

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Date:   Fri, 9 Sep 2022 09:54:07 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        Zhu Tony <tony.zhu@...el.com>, iommu@...ts.linux.dev,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 09/13] iommu/sva: Refactoring
 iommu_sva_bind/unbind_device()

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