On Mon, Dec 06, 2021 at 09:58:46AM +0800, Lu Baolu wrote:

quoted

From the perspective of who is initiating the device to do DMA, device

DMA could be divided into the following types:

        DMA_OWNER_DMA_API: Device DMAs are initiated by a kernel driver
			through the kernel DMA API.
        DMA_OWNER_PRIVATE_DOMAIN: Device DMAs are initiated by a kernel
			driver with its own PRIVATE domain.
	DMA_OWNER_PRIVATE_DOMAIN_USER: Device DMAs are initiated by
			userspace.

I have looked at the other iommu patches in this series, but I still
don't quite get what the difference in the code flow is between
DMA_OWNER_PRIVATE_DOMAIN and DMA_OWNER_PRIVATE_DOMAIN_USER. What are the
differences in the iommu core behavior based on this setting?

        int iommu_device_set_dma_owner(struct device *dev,
                enum iommu_dma_owner type, void *owner_cookie);
        void iommu_device_release_dma_owner(struct device *dev,
                enum iommu_dma_owner type);

It the owner is a group-wide setting, it should be called with the group
instead of the device. I have seen the group-specific funcitons are
added later, but that leaves the question why the device-specific ones
are needed at all.

+	enum iommu_dma_owner dma_owner;
+	refcount_t owner_cnt;
+	void *owner_cookie;
 };

I am also not quite happy yet with calling this dma_owner, but can't
come up with a better name yet.

DMA_OWNER_NONE is also questionable. All devices are always in one
domain, and the default domain is always the one used for DMA-API, so
why isn't the initial value DMA_OWNER_DMA_API?

Regards,

	Joerg