Re: [PATCH 08/12] iommufd/selftest: Put iopf enablement in domain attach path

[Baolu Lu]

On 2/20/25 09:02, Jason Gunthorpe wrote:
> On Fri, Feb 14, 2025 at 02:11:00PM +0800, Lu Baolu wrote:
> > @@ -197,11 +201,19 @@ static int mock_domain_nop_attach(struct iommu_domain *domain,
> >   	if (domain->dirty_ops && (mdev->flags & MOCK_FLAGS_DEVICE_NO_DIRTY))
> >   		return -EINVAL;
> >   
> > +	return mock_dev_enable_iopf(dev, domain);
> > +}
>
> This isn't going to work for a replace type operation? Maybe like:
>
> if (old_domain->iopf_handler && !domain->iopf_handler)
> 	return mock_dev_disable_iopf(dev, domain);
> if (old_domain->iopf_handler && domain->iopf_handler)
>          return 0;
> return mock_dev_enable_iopf(dev, domain);
>
> ?

The iommufd mock device driver appears not to support replacement. The
replacement operation on this driver is likely handled as follows:

- attach domain_a
- attach blocking_domain
- attach domain_b

The mock_dev_disable_iopf() is called in attach_dev of the blocking
domain.

There seems to be a bug in this patch. The existing domain should be
passed to mock_dev_disable_iopf().  It requires something similar to the
following:

diff --git a/drivers/iommu/iommufd/selftest.c 
b/drivers/iommu/iommufd/selftest.c
index a6b12cee7b00..54a6f0851758 100644
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -168,6 +168,7 @@ struct mock_dev {
        int id;
        u32 cache[MOCK_DEV_CACHE_NUM];
        unsigned int iopf_refcount;
+       struct iommu_domain *domain;
 };

 static inline struct mock_dev *to_mock_dev(struct device *dev)
@@ -197,17 +198,24 @@ static int mock_domain_nop_attach(struct 
iommu_domain *domain,
                                  struct device *dev)
 {
        struct mock_dev *mdev = to_mock_dev(dev);
+       int ret;

        if (domain->dirty_ops && (mdev->flags & 
MOCK_FLAGS_DEVICE_NO_DIRTY))
                return -EINVAL;

-       return mock_dev_enable_iopf(dev, domain);
+       ret = mock_dev_enable_iopf(dev, domain);
+       if (ret)
+               return ret;
+
+       mdev->domain = domain;
 }

 static int mock_domain_blocking_attach(struct iommu_domain *domain,
                                       struct device *dev)
 {
-       mock_dev_disable_iopf(dev, domain);
+       struct mock_dev *mdev = to_mock_dev(dev);
+
+       mock_dev_disable_iopf(dev, mdev->domain);

        return 0;
 }

Thanks,
baolu