On Mon, 2020-11-23 at 12:32 +0000, Will Deacon wrote: > 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; > }
Thanks for your quick review. I have fixed and tested it. the patch is simple. I copy it here. Is this readable for you now? --- 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 map_size = 0; if (domain->ops->apply_resv_region) domain->ops->apply_resv_region(dev, domain, entry); @@ -752,12 +753,21 @@ 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) - continue; + if (!phys_addr) { + map_size += pg_size; + if (addr + pg_size < end) + continue; + else + addr += pg_size; /*Point to End */ + } - ret = iommu_map(domain, addr, addr, pg_size, entry->prot); - if (ret) - goto out; + if (map_size) { + ret = iommu_map(domain, addr - map_size, addr - map_size, + map_size, entry->prot); + if (ret) + goto out; + map_size = 0; + } } > > Will