Re: [PATCH v4 2/9] iommu: Replace sva_iommu with iommu_attach_handle

[Baolu Lu]

On 4/3/24 7:59 PM, Jason Gunthorpe wrote:
> On Wed, Apr 03, 2024 at 09:15:12AM +0800, Lu Baolu wrote:
> > +	/* A bond already exists, just take a reference`. */
> > +	handle = iommu_attach_handle_get(group, iommu_mm->pasid);
> > +	if (handle) {
> > +		mutex_unlock(&iommu_sva_lock);
> > +		return handle;
> >   	}
> At least in this context this is not enough we need to ensure that the
> domain on the PASID is actually an SVA domain and it was installed by
> this mechanism, not an iommufd domain for instance.
>
> ie you probably need a type field in the iommu_attach_handle to tell
> what the priv is.
>
> Otherwise this seems like a great idea!

Yes, you are right. For the SVA case, I will add the following changes.
The IOMMUFD path will also need such enhancement. I will update it in
the next version.

diff --git a/drivers/iommu/iommu-priv.h b/drivers/iommu/iommu-priv.h
index 08c0667cef54..9aee70f87a21 100644
--- a/drivers/iommu/iommu-priv.h
+++ b/drivers/iommu/iommu-priv.h
@@ -28,9 +28,22 @@ void iommu_device_unregister_bus(struct iommu_device 
*iommu,
 				 const struct bus_type *bus,
 				 struct notifier_block *nb);

+enum attach_handle_type {
+	ATTACH_HANDLE_TYPE_DEFAULT = 0,
+	ATTACH_HANDLE_TYPE_SVA,
+	ATTACH_HANDLE_TYPE_IOMMUFD,
+};
+
 struct iommu_attach_handle {
 	struct iommu_domain		*domain;
 	refcount_t			users;
+
+	/*
+	 * Set by the attach interface callers. The type field could be used
+	 * by the caller to identify whether the priv field was installed by
+	 * them.
+	 */
+	enum attach_handle_type		type;
 	void				*priv;
 };

diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index c66cf26137bf..3eb664cc3f3a 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -90,7 +90,11 @@ struct iommu_attach_handle 
*iommu_sva_bind_device(struct device *dev, struct mm_
 	handle = iommu_attach_handle_get(group, iommu_mm->pasid);
 	if (handle) {
 		mutex_unlock(&iommu_sva_lock);
-		return handle;
+		if (handle->type == ATTACH_HANDLE_TYPE_SVA)
+			return handle;
+
+		iommu_attach_handle_put(handle);
+		return ERR_PTR(-EBUSY);
 	}

 	/* Search for an existing domain. */
@@ -118,6 +122,7 @@ struct iommu_attach_handle 
*iommu_sva_bind_device(struct device *dev, struct mm_
 out:
 	handle = iommu_attach_handle_get(group, iommu_mm->pasid);
 	mutex_unlock(&iommu_sva_lock);
+	handle->type = ATTACH_HANDLE_TYPE_SVA;
 	handle->priv = dev;

 	return handle;

Best regards,
baolu