Hi Olav,
On Fri, Aug 01, 2014 at 01:54:44AM +0100, 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.
Just a couple of minor comments, but I think this is almost there now.
> Signed-off-by: Olav Haugan <ohaugan@xxxxxxxxxxxxxx>
> ---
> 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)
> +{
What do you anticipate passing in the flags parameter? I assume it's
something specific to the scatterlist, since we can't provide this to
iommu_map as it stands?
> + 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;
> + }
> + } 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);
I think this would be cleaner if you stuck it in the loop above and removed
all these labels:
if (ret) {
iommu_unmap(...);
break;
}
Will
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