iommu/amd: Sync once for scatter-gather operations

On virtual machines, software must flush the IOTLB after each page table
entry update.

The iommu_map_sg() code iterates through the given scatter-gather list
and invokes iommu_map() for each element in the scatter-gather list,
which calls into the vendor IOMMU driver through iommu_ops callback. As
the result, a single sg mapping may lead to multiple IOTLB flushes.

Fix this by adding amd_iotlb_sync_map() callback and flushing at this
point after all sg mappings we set.

This commit is followed and inspired by commit 933fcd01e97e2
("iommu/vt-d: Add iotlb_sync_map callback").

Cc: Joerg Roedel <joro@8bytes.org>
Cc: Will Deacon <will@kernel.org>
Cc: Jiajun Cao <caojiajun@vmware.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Nadav Amit <namit@vmware.com>
Link: https://lore.kernel.org/r/20210723093209.714328-7-namit@vmware.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 0957be3..cee91cd 100644 (file)
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2028,6 +2028,16 @@ static int amd_iommu_attach_device(struct iommu_domain *dom,
        return ret;
 }
 
+static void amd_iommu_iotlb_sync_map(struct iommu_domain *dom,
+                                    unsigned long iova, size_t size)
+{
+       struct protection_domain *domain = to_pdomain(dom);
+       struct io_pgtable_ops *ops = &domain->iop.iop.ops;
+
+       if (ops->map)
+               domain_flush_np_cache(domain, iova, size);
+}
+
 static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
                         phys_addr_t paddr, size_t page_size, int iommu_prot,
                         gfp_t gfp)
@@ -2046,10 +2056,8 @@ static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
        if (iommu_prot & IOMMU_WRITE)
                prot |= IOMMU_PROT_IW;
 
-       if (ops->map) {
+       if (ops->map)
                ret = ops->map(ops, iova, paddr, page_size, prot, gfp);
-               domain_flush_np_cache(domain, iova, page_size);
-       }
 
        return ret;
 }
@@ -2229,6 +2237,7 @@ const struct iommu_ops amd_iommu_ops = {
        .attach_dev = amd_iommu_attach_device,
        .detach_dev = amd_iommu_detach_device,
        .map = amd_iommu_map,
+       .iotlb_sync_map = amd_iommu_iotlb_sync_map,
        .unmap = amd_iommu_unmap,
        .iova_to_phys = amd_iommu_iova_to_phys,
        .probe_device = amd_iommu_probe_device,