linux-kernel - Re: [PATCH v10 5/6] iommu: Support mm PASID 1:n with sva domains

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Message-ID: <CABQgh9GxQmGU2HR73bSoZLuf4XZFhThXwUs_HJx6KwxDmXrXgg@mail.gmail.com>
Date: Wed, 21 Feb 2024 09:28:07 +0800
From: Zhangfei Gao <zhangfei.gao@...aro.org>
To: "Zhang, Tina" <tina.zhang@...el.com>
Cc: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, David Woodhouse <dwmw2@...radead.org>, 
	Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>, 
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>, Jason Gunthorpe <jgg@...pe.ca>, 
	"Tian, Kevin" <kevin.tian@...el.com>, Nicolin Chen <nicolinc@...dia.com>, 
	Michael Shavit <mshavit@...gle.com>, Vasant Hegde <vasant.hegde@....com>, 
	Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v10 5/6] iommu: Support mm PASID 1:n with sva domains

Hi, Tina

On Wed, 21 Feb 2024 at 07:58, Zhang, Tina <tina.zhang@...el.com> wrote:

> > >  struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct
> > > mm_struct *mm)  {
> > > +       struct iommu_mm_data *iommu_mm;
> > >         struct iommu_domain *domain;
> > >         struct iommu_sva *handle;
> > >         int ret;
> > >
> > > +       mutex_lock(&iommu_sva_lock);
> > > +
> > >         /* Allocate mm->pasid if necessary. */
> > > -       ret = iommu_sva_alloc_pasid(mm, dev);
> > > -       if (ret)
> > > -               return ERR_PTR(ret);
> > > +       iommu_mm = iommu_alloc_mm_data(mm, dev);
> > > +       if (IS_ERR(iommu_mm)) {
> > > +               ret = PTR_ERR(iommu_mm);
> > > +               goto out_unlock;
> > > +       }
> > >
> > >         handle = kzalloc(sizeof(*handle), GFP_KERNEL);
> > > -       if (!handle)
> > > -               return ERR_PTR(-ENOMEM);
> > > -
> > > -       mutex_lock(&iommu_sva_lock);
> > > -       /* Search for an existing domain. */
> > > -       domain = iommu_get_domain_for_dev_pasid(dev, mm->pasid,
> > > -                                               IOMMU_DOMAIN_SVA);
> > > -       if (IS_ERR(domain)) {
> > > -               ret = PTR_ERR(domain);
> > > +       if (!handle) {
> > > +               ret = -ENOMEM;
> > >                 goto out_unlock;
> > >         }
> > >
> > > -       if (domain) {
> > > -               domain->users++;
> > > -               goto out;
> >
> > Our multi bind test case broke since 6.8-rc1.
> > The test case can use same domain & pasid, return different handle,
> > 6.7 simply  domain->users ++ and return.
> >
> > > +       /* Search for an existing domain. */
> > > +       list_for_each_entry(domain, &mm->iommu_mm->sva_domains, next)
> > {
> > > +               ret = iommu_attach_device_pasid(domain, dev,
> > > + iommu_mm->pasid);
> >
> > Now iommu_attach_device_pasid return BUSY since the same pasid.
> > And then iommu_sva_bind_device attach ret=-16
> Sounds like the test case tries to bind a device to a same mm multiple times without unbinding the device and the expectation is that it can always return a valid handle to pass the test. Right?

Yes

The device can bind to the same mm multi-times and return different handle,
Since the refcount, no need to unbind and bind sequently,
The unbind can happen later with the handle.

Thanks