[PATCH v4 9/9] iommu/vt-d: Use bounce buffer for untrusted devices

[Lu Baolu]

The Intel VT-d hardware uses paging for DMA remapping.
The minimum mapped window is a page size. The device
drivers may map buffers not filling the whole IOMMU
window. This allows the device to access to possibly
unrelated memory and a malicious device could exploit
this to perform DMA attacks. To address this, the
Intel IOMMU driver will use bounce pages for those
buffers which don't fill whole IOMMU pages.

Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Tested-by: Xu Pengfei <pengfei.xu@xxxxxxxxx>
Tested-by: Mika Westerberg <mika.westerberg@xxxxxxxxx>
---
 drivers/iommu/intel-iommu.c | 128 ++++++++++++++++++++++++++++++++----
 1 file changed, 117 insertions(+), 11 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 2f54734d1c43..4bf744a1c239 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -52,6 +52,7 @@
 #include <asm/irq_remapping.h>
 #include <asm/cacheflush.h>
 #include <asm/iommu.h>
+#include <trace/events/intel_iommu.h>
 
 #include "irq_remapping.h"
 #include "intel-pasid.h"
@@ -3537,6 +3538,19 @@ __intel_map_single(struct device *dev, phys_addr_t paddr, size_t size,
 	if (!iova_pfn)
 		goto error;
 
+	if (device_needs_bounce(dev)) {
+		dma_addr_t ret_addr;
+
+		ret_addr = iommu_bounce_map(dev, iova_pfn << PAGE_SHIFT,
+					    paddr, size, dir, attrs);
+		if (ret_addr == DMA_MAPPING_ERROR)
+			goto error;
+		trace_bounce_map_single(dev, iova_pfn << PAGE_SHIFT,
+					paddr, size);
+
+		return ret_addr;
+	}
+
 	/*
 	 * Check if DMAR supports zero-length reads on write only
 	 * mappings..
@@ -3620,14 +3634,28 @@ static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size,
 		start_pfn = mm_to_dma_pfn(iova_pfn);
 		last_pfn = start_pfn + nrpages - 1;
 
-		freelist = domain_unmap(domain, start_pfn, last_pfn);
+		if (device_needs_bounce(dev))
+			for_each_sg(sglist, sg, nelems, i) {
+				iommu_bounce_unmap(dev, sg_dma_address(sg),
+						   sg->length, dir, attrs);
+				trace_bounce_unmap_sg(dev, i, nelems,
+						      sg_dma_address(sg),
+						      sg_phys(sg), sg->length);
+			}
+		else
+			freelist = domain_unmap(domain, start_pfn, last_pfn);
 	} else {
 		iova_pfn = IOVA_PFN(dev_addr);
 		nrpages = aligned_nrpages(dev_addr, size);
 		start_pfn = mm_to_dma_pfn(iova_pfn);
 		last_pfn = start_pfn + nrpages - 1;
 
-		freelist = domain_unmap(domain, start_pfn, last_pfn);
+		if (device_needs_bounce(dev)) {
+			iommu_bounce_unmap(dev, dev_addr, size, dir, attrs);
+			trace_bounce_unmap_single(dev, dev_addr, size);
+		} else {
+			freelist = domain_unmap(domain, start_pfn, last_pfn);
+		}
 	}
 
 	if (dev_is_pci(dev))
@@ -3774,6 +3802,26 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele
 		prot |= DMA_PTE_WRITE;
 
 	start_vpfn = mm_to_dma_pfn(iova_pfn);
+	if (device_needs_bounce(dev)) {
+		for_each_sg(sglist, sg, nelems, i) {
+			dma_addr_t ret_addr;
+
+			ret_addr = iommu_bounce_map(dev,
+					start_vpfn << VTD_PAGE_SHIFT,
+					sg_phys(sg), sg->length, dir, attrs);
+			if (ret_addr == DMA_MAPPING_ERROR)
+				break;
+
+			trace_bounce_map_sg(dev, i, nelems, ret_addr,
+					    sg_phys(sg), sg->length);
+
+			sg->dma_address = ret_addr;
+			sg->dma_length = sg->length;
+			start_vpfn += aligned_nrpages(sg->offset, sg->length);
+		}
+
+		return i;
+	}
 
 	ret = domain_sg_mapping(domain, start_vpfn, sglist, size, prot);
 	if (unlikely(ret)) {
@@ -3787,16 +3835,74 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele
 	return nelems;
 }
 
+static void
+intel_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
+			  size_t size, enum dma_data_direction dir)
+{
+	if (!iommu_need_mapping(dev))
+		dma_direct_sync_single_for_cpu(dev, addr, size, dir);
+
+	if (device_needs_bounce(dev))
+		iommu_bounce_sync(dev, addr, size, dir, SYNC_FOR_CPU);
+}
+
+static void
+intel_sync_single_for_device(struct device *dev, dma_addr_t addr,
+			     size_t size, enum dma_data_direction dir)
+{
+	if (!iommu_need_mapping(dev))
+		dma_direct_sync_single_for_device(dev, addr, size, dir);
+
+	if (device_needs_bounce(dev))
+		iommu_bounce_sync(dev, addr, size, dir, SYNC_FOR_DEVICE);
+}
+
+static void
+intel_sync_sg_for_cpu(struct device *dev, struct scatterlist *sglist,
+		      int nelems, enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	if (!iommu_need_mapping(dev))
+		dma_direct_sync_sg_for_cpu(dev, sglist, nelems, dir);
+
+	if (device_needs_bounce(dev))
+		for_each_sg(sglist, sg, nelems, i)
+			iommu_bounce_sync(dev, sg_dma_address(sg),
+					  sg_dma_len(sg), dir, SYNC_FOR_CPU);
+}
+
+static void
+intel_sync_sg_for_device(struct device *dev, struct scatterlist *sglist,
+			 int nelems, enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	if (!iommu_need_mapping(dev))
+		dma_direct_sync_sg_for_device(dev, sglist, nelems, dir);
+
+	if (device_needs_bounce(dev))
+		for_each_sg(sglist, sg, nelems, i)
+			iommu_bounce_sync(dev, sg_dma_address(sg),
+					  sg_dma_len(sg), dir, SYNC_FOR_DEVICE);
+}
+
 static const struct dma_map_ops intel_dma_ops = {
-	.alloc = intel_alloc_coherent,
-	.free = intel_free_coherent,
-	.map_sg = intel_map_sg,
-	.unmap_sg = intel_unmap_sg,
-	.map_page = intel_map_page,
-	.unmap_page = intel_unmap_page,
-	.map_resource = intel_map_resource,
-	.unmap_resource = intel_unmap_resource,
-	.dma_supported = dma_direct_supported,
+	.alloc			= intel_alloc_coherent,
+	.free			= intel_free_coherent,
+	.map_sg			= intel_map_sg,
+	.unmap_sg		= intel_unmap_sg,
+	.map_page		= intel_map_page,
+	.unmap_page		= intel_unmap_page,
+	.sync_single_for_cpu	= intel_sync_single_for_cpu,
+	.sync_single_for_device	= intel_sync_single_for_device,
+	.sync_sg_for_cpu	= intel_sync_sg_for_cpu,
+	.sync_sg_for_device	= intel_sync_sg_for_device,
+	.map_resource		= intel_map_resource,
+	.unmap_resource		= intel_unmap_resource,
+	.dma_supported		= dma_direct_supported,
 };
 
 static inline int iommu_domain_cache_init(void)
-- 
2.17.1