[PATCH v4 1/1] iommu-api: Add map_sg/unmap_sg functions

[Konrad Rzeszutek Wilk]

On Thu, Jul 31, 2014 at 05:54:44PM -0700, Olav Haugan wrote:
> Mapping and unmapping are more often than not in the critical path.
> map_sg and unmap_sg allows IOMMU driver implementations to optimize
> the process of mapping and unmapping buffers into the IOMMU page tables.
> 
> Instead of mapping a buffer one page at a time and requiring potentially
> expensive TLB operations for each page, this function allows the driver
> to map all pages in one go and defer TLB maintenance until after all
> pages have been mapped.
> 
> Additionally, the mapping operation would be faster in general since
> clients does not have to keep calling map API over and over again for
> each physically contiguous chunk of memory that needs to be mapped to a
> virtually contiguous region.

That is assuming that physical == bus topology.

> 
> Signed-off-by: Olav Haugan <ohaugan at codeaurora.org>
> ---
>  drivers/iommu/iommu.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/iommu.h | 28 ++++++++++++++++++++++++++++
>  2 files changed, 72 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 1698360..1d5dc2e 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1088,6 +1088,50 @@ size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova, size_t size)
>  }
>  EXPORT_SYMBOL_GPL(iommu_unmap);
>  
> +int iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
> +			struct scatterlist *sg, unsigned int nents,
> +			int prot, unsigned long flags)
> +{
> +	int ret = 0;
> +	unsigned long offset = 0;
> +
> +	if (unlikely(domain->ops->map_sg == NULL)) {
> +		unsigned int i;
> +		struct scatterlist *s;
> +
> +		for_each_sg(sg, s, nents, i) {
> +			phys_addr_t phys = page_to_phys(sg_page(s));
> +			size_t page_len = s->offset + s->length;
> +
> +			ret = iommu_map(domain, iova + offset, phys, page_len,
> +					prot);
> +			if (ret)
> +				goto fail;
> +
> +			offset += page_len;
> +		}

I think it would be better if you had an 'default_iommu_map_sg' with
the implementation above. And then the default ops->map_sg would point to
that and each IOMMU would over-write with its own version.

That way you don't need any of this 'if' and can have the 'iommu_map_sg'
be in the header file (either as static inline or an macro).


> +	} else {
> +		ret = domain->ops->map_sg(domain, iova, sg, nents, prot, flags);
> +	}
> +	goto out;
> +
> +fail:
> +	/* undo mappings already done in case of error */
> +	iommu_unmap(domain, iova, offset);
> +out:
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_map_sg);
> +
> +int iommu_unmap_sg(struct iommu_domain *domain, unsigned long iova,
> +			size_t size, unsigned long flags)
> +{
> +	if (unlikely(domain->ops->unmap_sg == NULL))
> +		return iommu_unmap(domain, iova, size);
> +	else
> +		return domain->ops->unmap_sg(domain, iova, size, flags);
> +}
> +EXPORT_SYMBOL_GPL(iommu_unmap_sg);
>  
>  int iommu_domain_window_enable(struct iommu_domain *domain, u32 wnd_nr,
>  			       phys_addr_t paddr, u64 size, int prot)
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 20f9a52..66ad543 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -22,6 +22,7 @@
>  #include <linux/errno.h>
>  #include <linux/err.h>
>  #include <linux/types.h>
> +#include <linux/scatterlist.h>
>  #include <trace/events/iommu.h>
>  
>  #define IOMMU_READ	(1 << 0)
> @@ -93,6 +94,10 @@ enum iommu_attr {
>   * @detach_dev: detach device from an iommu domain
>   * @map: map a physically contiguous memory region to an iommu domain
>   * @unmap: unmap a physically contiguous memory region from an iommu domain
> + * @map_sg: map a scatter-gather list of physically contiguous memory chunks
> + * to an iommu domain
> + * @unmap_sg: unmap a scatter-gather list of physically contiguous memory
> + * chunks from an iommu domain
>   * @iova_to_phys: translate iova to physical address
>   * @domain_has_cap: domain capabilities query
>   * @add_device: add device to iommu grouping
> @@ -110,6 +115,11 @@ struct iommu_ops {
>  		   phys_addr_t paddr, size_t size, int prot);
>  	size_t (*unmap)(struct iommu_domain *domain, unsigned long iova,
>  		     size_t size);
> +	int (*map_sg)(struct iommu_domain *domain, unsigned long iova,
> +			struct scatterlist *sg, unsigned int nents, int prot,
> +			unsigned long flags);
> +	int (*unmap_sg)(struct iommu_domain *domain, unsigned long iova,
> +			size_t size, unsigned long flags);
>  	phys_addr_t (*iova_to_phys)(struct iommu_domain *domain, dma_addr_t iova);
>  	int (*domain_has_cap)(struct iommu_domain *domain,
>  			      unsigned long cap);
> @@ -153,6 +163,11 @@ extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
>  		     phys_addr_t paddr, size_t size, int prot);
>  extern size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova,
>  		       size_t size);
> +extern int iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
> +			struct scatterlist *sg, unsigned int nents, int prot,
> +			unsigned long flags);
> +extern int iommu_unmap_sg(struct iommu_domain *domain, unsigned long iova,
> +				size_t size, unsigned long flags);
>  extern phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain, dma_addr_t iova);
>  extern int iommu_domain_has_cap(struct iommu_domain *domain,
>  				unsigned long cap);
> @@ -287,6 +302,19 @@ static inline int iommu_unmap(struct iommu_domain *domain, unsigned long iova,
>  	return -ENODEV;
>  }
>  
> +static inline int iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
> +			struct scatterlist *sg, unsigned int nents, int prot,
> +			unsigned long flags)
> +{
> +	return -ENODEV;
> +}
> +
> +static inline int iommu_unmap_sg(struct iommu_domain *domain,
> +			unsigned long iova, size_t size, unsigned long flags)
> +{
> +	return -ENODEV;
> +}
> +
>  static inline int iommu_domain_window_enable(struct iommu_domain *domain,
>  					     u32 wnd_nr, phys_addr_t paddr,
>  					     u64 size, int prot)
> -- 
> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> hosted by The Linux Foundation
> 
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