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Subject[PATCH v6 6/7] iommu/amd: Sync once for scatter-gather operations
Date
From: Nadav Amit <namit@vmware.com>

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>
---
drivers/iommu/amd/iommu.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index f5d5f2124391..7846fcb1e92b 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2022,6 +2022,16 @@ 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)
@@ -2040,10 +2050,8 @@ 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;
}
@@ -2223,6 +2231,7 @@ 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,
--
2.25.1
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