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SubjectRe: [PATCH v1 8/9] iommu: Introduce iotlb_sync_map callback
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On 08/05/18 19:16, Dmitry Osipenko wrote:
> Introduce iotlb_sync_map() callback that is invoked in the end of
> iommu_map(). This new callback allows IOMMU drivers to avoid syncing
> on mapping of each contiguous chunk and sync only when whole mapping
> is completed, optimizing performance of the mapping operation.

This looks like a reasonable compromise - for users of
IO_PGTABLE_QUIRK_TLBI_ON_MAP we can leave the implicit add_flush() in
place for each individual map call, but at least move the sync() out to
this callback, which should still be beneficial overall.

Modulo one possible nit below,

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/iommu/iommu.c | 8 ++++++--
> include/linux/iommu.h | 1 +
> 2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index d2aa23202bb9..39b2ee66aa96 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1508,13 +1508,14 @@ static size_t iommu_pgsize(struct iommu_domain *domain,
> int iommu_map(struct iommu_domain *domain, unsigned long iova,
> phys_addr_t paddr, size_t size, int prot)
> {
> + const struct iommu_ops *ops = domain->ops;
> unsigned long orig_iova = iova;
> unsigned int min_pagesz;
> size_t orig_size = size;
> phys_addr_t orig_paddr = paddr;
> int ret = 0;
>
> - if (unlikely(domain->ops->map == NULL ||
> + if (unlikely(ops->map == NULL ||
> domain->pgsize_bitmap == 0UL))
> return -ENODEV;
>
> @@ -1543,7 +1544,7 @@ int iommu_map(struct iommu_domain *domain, unsigned long iova,
> pr_debug("mapping: iova 0x%lx pa %pa pgsize 0x%zx\n",
> iova, &paddr, pgsize);
>
> - ret = domain->ops->map(domain, iova, paddr, pgsize, prot);
> + ret = ops->map(domain, iova, paddr, pgsize, prot);
> if (ret)
> break;
>
> @@ -1552,6 +1553,9 @@ int iommu_map(struct iommu_domain *domain, unsigned long iova,
> size -= pgsize;
> }
>
> + if (ops->iotlb_sync_map)
> + ops->iotlb_sync_map(domain);

Is it worth trying to skip this in the error case when we're just going
to undo it immediately?

Robin.

> +
> /* unroll mapping in case something went wrong */
> if (ret)
> iommu_unmap(domain, orig_iova, orig_size - size);
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 19938ee6eb31..5224aa376377 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -206,6 +206,7 @@ struct iommu_ops {
> void (*flush_iotlb_all)(struct iommu_domain *domain);
> void (*iotlb_range_add)(struct iommu_domain *domain,
> unsigned long iova, size_t size);
> + void (*iotlb_sync_map)(struct iommu_domain *domain);
> void (*iotlb_sync)(struct iommu_domain *domain);
> phys_addr_t (*iova_to_phys)(struct iommu_domain *domain, dma_addr_t iova);
> int (*add_device)(struct device *dev);
>

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