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

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Message-ID: <d93c8cc9-77a5-4b78-85d2-6b4601f52266@linux.intel.com>
Date: Thu, 20 Feb 2025 15:03:21 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>, Kevin Tian <kevin.tian@...el.com>,
 Fenghua Yu <fenghua.yu@...el.com>, Dave Jiang <dave.jiang@...el.com>,
 Vinod Koul <vkoul@...nel.org>, Zhangfei Gao <zhangfei.gao@...aro.org>,
 Zhou Wang <wangzhou1@...ilicon.com>, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/12] iommufd/selftest: Put iopf enablement in domain
 attach path

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