On Fri, Nov 20, 2020 at 05:06:28PM +0800, Yong Wu wrote:
> Currently direct_mapping always use the smallest pgsize which is SZ_4K
> normally to mapping. This is unnecessary. we could gather the size, and
> call iommu_map then, iommu_map could decide how to map better with the
> just right pgsize.
>
> From the original comment, we should take care overlap, otherwise,
> iommu_map may return -EEXIST. In this overlap case, we should map the
> previous region before overlap firstly. then map the left part.
>
> Each a iommu device will call this direct_mapping when its iommu
> initialize, This patch is effective to improve the boot/initialization
> time especially while it only needs level 1 mapping.
>
> Signed-off-by: Anan Sun <anan....@mediatek.com>
> Signed-off-by: Yong Wu <yong...@mediatek.com>
> ---
> drivers/iommu/iommu.c | 20 ++++++++++++++++++--
> 1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index df87c8e825f7..854a8fcb928d 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -737,6 +737,7 @@ static int iommu_create_device_direct_mappings(struct
> iommu_group *group,
> /* We need to consider overlapping regions for different devices */
> list_for_each_entry(entry, &mappings, list) {
> dma_addr_t start, end, addr;
> + size_t unmapped_sz = 0;
I think "unmapped" is the wrong word here, as this variable actually
represents the amount we want to map! I suggest "map_size" instead.
> if (domain->ops->apply_resv_region)
> domain->ops->apply_resv_region(dev, domain, entry);
> @@ -752,10 +753,25 @@ static int iommu_create_device_direct_mappings(struct
> iommu_group *group,
> phys_addr_t phys_addr;
>
> phys_addr = iommu_iova_to_phys(domain, addr);
> - if (phys_addr)
> + if (phys_addr == 0) {
> + unmapped_sz += pg_size; /* Gather the size. */
> continue;
> + }
>
> - ret = iommu_map(domain, addr, addr, pg_size,
> entry->prot);
> + if (unmapped_sz) {
> + /* Map the region before the overlap. */
> + ret = iommu_map(domain, start, start,
> + unmapped_sz, entry->prot);
> + if (ret)
> + goto out;
> + start += unmapped_sz;
I think it's a bit confusing to update start like this. Can we call
iommu_map(domain, addr - map_size, addr - map_size, map_size, entry->prot)
instead?
> + unmapped_sz = 0;
> + }
> + start += pg_size;
> + }
> + if (unmapped_sz) {
> + ret = iommu_map(domain, start, start, unmapped_sz,
> + entry->prot);
Can you avoid this hunk by changing your loop check to something like:
if (!phys_addr) {
map_size += pg_size;
if (addr + pg_size < end)
continue;
}
Will
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