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SubjectRe: [PATCH 10/22] iommu: Introduce direct mapped region handling
On 28/05/15 17:41, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
>
> Add two new functions to the IOMMU-API to allow the IOMMU
> drivers to export the requirements for direct mapped regions
> per device.
> This is useful for exporting the information in Intel VT-d's
> RMRR entries or AMD-Vi's unity mappings.

Whilst I agree with the utility of a common abstraction for the IOMMU
core to use (I think we could easily turn Marek's proposal for ARM[1]
into a generic of_iommu_ backend for this), I'm less convinced that it
needs to be exported as part of the API.

I was envisioning eventually moving the IOVA data inside the
iommu_domain itself for the managed DMA-API implementation, so that the
IOMMU core would be responsible for setting it up. Then the core just
needs to ask the driver about any relevant reservations as it creates a
domain/attaches a device, and the callers can remain in blissful
ignorance. Besides, beyond probe time, I don't see many good reasons at
all for a caller to have a struct device for something, yet not have
taken control of any DMA the firmware left running.

Is that at odds with your ideas?

Robin.

[1]:http://article.gmane.org/gmane.linux.kernel.samsung-soc/45429

> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
> drivers/iommu/iommu.c | 16 ++++++++++++++++
> include/linux/iommu.h | 31 +++++++++++++++++++++++++++++++
> 2 files changed, 47 insertions(+)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index a0a38bd..6b8d6e7 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1469,3 +1469,19 @@ int iommu_domain_set_attr(struct iommu_domain *domain,
> return ret;
> }
> EXPORT_SYMBOL_GPL(iommu_domain_set_attr);
> +
> +void iommu_get_dm_regions(struct device *dev, struct list_head *list)
> +{
> + const struct iommu_ops *ops = dev->bus->iommu_ops;
> +
> + if (ops && ops->get_dm_regions)
> + ops->get_dm_regions(dev, list);
> +}
> +
> +void iommu_put_dm_regions(struct device *dev, struct list_head *list)
> +{
> + const struct iommu_ops *ops = dev->bus->iommu_ops;
> +
> + if (ops && ops->put_dm_regions)
> + ops->put_dm_regions(dev, list);
> +}
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 683a1c4..6894999 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -114,6 +114,20 @@ enum iommu_attr {
> DOMAIN_ATTR_MAX,
> };
>
> +/**
> + * struct iommu_dm_region - descriptor for a direct mapped memory region
> + * @list: Linked list pointers
> + * @start: System physical start address of the region
> + * @length: Length of the region in bytes
> + * @prot: IOMMU Protection flags (READ/WRITE/...)
> + */
> +struct iommu_dm_region {
> + struct list_head list;
> + phys_addr_t start;
> + size_t length;
> + int prot;
> +};
> +
> #ifdef CONFIG_IOMMU_API
>
> /**
> @@ -159,6 +173,10 @@ struct iommu_ops {
> int (*domain_set_attr)(struct iommu_domain *domain,
> enum iommu_attr attr, void *data);
>
> + /* Request/Free a list of direct mapping requirements for a device */
> + void (*get_dm_regions)(struct device *dev, struct list_head *list);
> + void (*put_dm_regions)(struct device *dev, struct list_head *list);
> +
> /* Window handling functions */
> int (*domain_window_enable)(struct iommu_domain *domain, u32 wnd_nr,
> phys_addr_t paddr, u64 size, int prot);
> @@ -205,6 +223,9 @@ extern phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain, dma_addr_t io
> extern void iommu_set_fault_handler(struct iommu_domain *domain,
> iommu_fault_handler_t handler, void *token);
>
> +extern void iommu_get_dm_regions(struct device *dev, struct list_head *list);
> +extern void iommu_put_dm_regions(struct device *dev, struct list_head *list);
> +
> extern int iommu_attach_group(struct iommu_domain *domain,
> struct iommu_group *group);
> extern void iommu_detach_group(struct iommu_domain *domain,
> @@ -379,6 +400,16 @@ static inline void iommu_set_fault_handler(struct iommu_domain *domain,
> {
> }
>
> +static inline void iommu_get_dm_regions(struct device *dev,
> + struct list_head *list)
> +{
> +}
> +
> +static inline void iommu_put_dm_regions(struct device *dev,
> + struct list_head *list)
> +{
> +}
> +
> static inline int iommu_attach_group(struct iommu_domain *domain,
> struct iommu_group *group)
> {
>



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