iommu/vt-d: only unmap mapped entries

Current unmap implementation unmaps the entire area covered by the IOVA
range, which is a power-of-2 aligned region. The corresponding map,
however, only maps those pages originally mapped by the user. This
discrepancy can lead to unmapping of already unmapped entries, which is
unneeded work.

With this patch, only mapped pages are unmapped. This is also a baseline
for a map/unmap implementation based on IOVAs and not iova structures,
which will allow caching.
Signed-off-by: Omer Peleg <omer@cs.technion.ac.il>
[mad@cs.technion.ac.il: rebased and reworded the commit message]
Signed-off-by: Adam Morrison <mad@cs.technion.ac.il>
Reviewed-by: Shaohua Li <shli@fb.com>
Reviewed-by: Ben Serebrin <serebrin@google.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/iommu/intel-iommu.c

@@ -459,6 +459,7 @@ static void flush_unmaps_timeout(unsigned long data);
 
 struct deferred_flush_entry {
 	struct iova *iova;
+	unsigned long nrpages;
 	struct dmar_domain *domain;
 	struct page *freelist;
 };
@@ -3542,6 +3543,7 @@ static void flush_unmaps(struct deferred_flush_data *flush_data)
 			struct deferred_flush_entry *entry =
 						&flush_table->entries[j];
 			struct iova *iova = entry->iova;
+			unsigned long nrpages = entry->nrpages;
 			struct dmar_domain *domain = entry->domain;
 			struct page *freelist = entry->freelist;
 
@@ -3549,10 +3551,9 @@ static void flush_unmaps(struct deferred_flush_data *flush_data)
 			if (cap_caching_mode(iommu->cap))
 				iommu_flush_iotlb_psi(iommu, domain,
 					mm_to_dma_pfn(iova->pfn_lo),
-					mm_to_dma_pfn(iova_size(iova)),
-					!freelist, 0);
+					nrpages, !freelist, 0);
 			else {
-				mask = ilog2(mm_to_dma_pfn(iova_size(iova)));
+				mask = ilog2(nrpages);
 				iommu_flush_dev_iotlb(domain,
 						(uint64_t)iova->pfn_lo << PAGE_SHIFT, mask);
 			}
@@ -3576,7 +3577,8 @@ static void flush_unmaps_timeout(unsigned long cpuid)
 	spin_unlock_irqrestore(&flush_data->lock, flags);
 }
 
-static void add_unmap(struct dmar_domain *dom, struct iova *iova, struct page *freelist)
+static void add_unmap(struct dmar_domain *dom, struct iova *iova,
+		      unsigned long nrpages, struct page *freelist)
 {
 	unsigned long flags;
 	int entry_id, iommu_id;
@@ -3610,6 +3612,7 @@ static void add_unmap(struct dmar_domain *dom, struct iova *iova, struct page *f
 	entry = &flush_data->tables[iommu_id].entries[entry_id];
 	entry->domain = dom;
 	entry->iova = iova;
+	entry->nrpages = nrpages;
 	entry->freelist = freelist;
 
 	if (!flush_data->timer_on) {
@@ -3622,10 +3625,11 @@ static void add_unmap(struct dmar_domain *dom, struct iova *iova, struct page *f
 	put_cpu();
 }
 
-static void intel_unmap(struct device *dev, dma_addr_t dev_addr)
+static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size)
 {
 	struct dmar_domain *domain;
 	unsigned long start_pfn, last_pfn;
+	unsigned long nrpages;
 	struct iova *iova;
 	struct intel_iommu *iommu;
 	struct page *freelist;
@@ -3643,8 +3647,9 @@ static void intel_unmap(struct device *dev, dma_addr_t dev_addr)
 		      (unsigned long long)dev_addr))
 		return;
 
+	nrpages = aligned_nrpages(dev_addr, size);
 	start_pfn = mm_to_dma_pfn(iova->pfn_lo);
-	last_pfn = mm_to_dma_pfn(iova->pfn_hi + 1) - 1;
+	last_pfn = start_pfn + nrpages - 1;
 
 	pr_debug("Device %s unmapping: pfn %lx-%lx\n",
 		 dev_name(dev), start_pfn, last_pfn);
@@ -3653,12 +3658,12 @@ static void intel_unmap(struct device *dev, dma_addr_t dev_addr)
 
 	if (intel_iommu_strict) {
 		iommu_flush_iotlb_psi(iommu, domain, start_pfn,
-				      last_pfn - start_pfn + 1, !freelist, 0);
+				      nrpages, !freelist, 0);
 		/* free iova */
 		__free_iova(&domain->iovad, iova);
 		dma_free_pagelist(freelist);
 	} else {
-		add_unmap(domain, iova, freelist);
+		add_unmap(domain, iova, nrpages, freelist);
 		/*
 		 * queue up the release of the unmap to save the 1/6th of the
 		 * cpu used up by the iotlb flush operation...
@@ -3670,7 +3675,7 @@ static void intel_unmap_page(struct device *dev, dma_addr_t dev_addr,
 			     size_t size, enum dma_data_direction dir,
 			     struct dma_attrs *attrs)
 {
-	intel_unmap(dev, dev_addr);
+	intel_unmap(dev, dev_addr, size);
 }
 
 static void *intel_alloc_coherent(struct device *dev, size_t size,
@@ -3729,7 +3734,7 @@ static void intel_free_coherent(struct device *dev, size_t size, void *vaddr,
 	size = PAGE_ALIGN(size);
 	order = get_order(size);
 
-	intel_unmap(dev, dma_handle);
+	intel_unmap(dev, dma_handle, size);
 	if (!dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT))
 		__free_pages(page, order);
 }
@@ -3738,7 +3743,16 @@ static void intel_unmap_sg(struct device *dev, struct scatterlist *sglist,
 			   int nelems, enum dma_data_direction dir,
 			   struct dma_attrs *attrs)
 {
-	intel_unmap(dev, sglist[0].dma_address);
+	dma_addr_t startaddr = sg_dma_address(sglist) & PAGE_MASK;
+	unsigned long nrpages = 0;
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sglist, sg, nelems, i) {
+		nrpages += aligned_nrpages(sg_dma_address(sg), sg_dma_len(sg));
+	}
+
+	intel_unmap(dev, startaddr, nrpages << VTD_PAGE_SHIFT);
 }
 
 static int intel_nontranslate_map_sg(struct device *hddev,