iommu/core: split mapping to page sizes as supported by the hardware

When mapping a memory region, split it to page sizes as supported
by the iommu hardware. Always prefer bigger pages, when possible,
in order to reduce the TLB pressure.

The logic to do that is now added to the IOMMU core, so neither the iommu
drivers themselves nor users of the IOMMU API have to duplicate it.

This allows a more lenient granularity of mappings; traditionally the
IOMMU API took 'order' (of a page) as a mapping size, and directly let
the low level iommu drivers handle the mapping, but now that the IOMMU
core can split arbitrary memory regions into pages, we can remove this
limitation, so users don't have to split those regions by themselves.

Currently the supported page sizes are advertised once and they then
remain static. That works well for OMAP and MSM but it would probably
not fly well with intel's hardware, where the page size capabilities
seem to have the potential to be different between several DMA
remapping devices.

register_iommu() currently sets a default pgsize behavior, so we can convert
the IOMMU drivers in subsequent patches. After all the drivers
are converted, the temporary default settings will be removed.

Mainline users of the IOMMU API (kvm and omap-iovmm) are adopted
to deal with bytes instead of page order.

Many thanks to Joerg Roedel <Joerg.Roedel@amd.com> for significant review!

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Cc: David Brown <davidb@codeaurora.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Joerg Roedel <Joerg.Roedel@amd.com>
Cc: Stepan Moskovchenko <stepanm@codeaurora.org>
Cc: KyongHo Cho <pullip.cho@samsung.com>
Cc: Hiroshi DOYU <hdoyu@nvidia.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 6 insertions, 11 deletions

diff --git a/drivers/iommu/omap-iovmm.c b/drivers/iommu/omap-iovmm.c
index e8fdb8830f69..0b7b14cb030b 100644
--- a/drivers/iommu/omap-iovmm.c
+++ b/drivers/iommu/omap-iovmm.c
@@ -409,7 +409,6 @@ static int map_iovm_area(struct iommu_domain *domain, struct iovm_struct *new,
         unsigned int i, j;
         struct scatterlist *sg;
         u32 da = new->da_start;
-        int order;
 
         if (!domain || !sgt)
                 return -EINVAL;
@@ -428,12 +427,10 @@ static int map_iovm_area(struct iommu_domain *domain, struct iovm_struct *new,
                 if (bytes_to_iopgsz(bytes) < 0)
                         goto err_out;
 
-                order = get_order(bytes);
-
                 pr_debug("%s: [%d] %08x %08x(%x)\n", __func__,
                          i, da, pa, bytes);
 
-                err = iommu_map(domain, da, pa, order, flags);
+                err = iommu_map(domain, da, pa, bytes, flags);
                 if (err)
                         goto err_out;
 
@@ -448,10 +445,9 @@ err_out:
                 size_t bytes;
 
                 bytes = sg->length + sg->offset;
-                order = get_order(bytes);
 
                 /* ignore failures.. we're already handling one */
-                iommu_unmap(domain, da, order);
+                iommu_unmap(domain, da, bytes);
 
                 da += bytes;
         }
@@ -466,7 +462,8 @@ static void unmap_iovm_area(struct iommu_domain *domain, struct omap_iommu *obj,
         size_t total = area->da_end - area->da_start;
         const struct sg_table *sgt = area->sgt;
         struct scatterlist *sg;
-        int i, err;
+        int i;
+        size_t unmapped;
 
         BUG_ON(!sgtable_ok(sgt));
         BUG_ON((!total) || !IS_ALIGNED(total, PAGE_SIZE));
@@ -474,13 +471,11 @@ static void unmap_iovm_area(struct iommu_domain *domain, struct omap_iommu *obj,
         start = area->da_start;
         for_each_sg(sgt->sgl, sg, sgt->nents, i) {
                 size_t bytes;
-                int order;
 
                 bytes = sg->length + sg->offset;
-                order = get_order(bytes);
 
-                err = iommu_unmap(domain, start, order);
-                if (err < 0)
+                unmapped = iommu_unmap(domain, start, bytes);
+                if (unmapped < bytes)
                         break;
 
                 dev_dbg(obj->dev, "%s: unmap %08x(%x) %08x\n",