[PATCH 1/2] vfio: Convert type1 iommu to use rbtree

[Alex Williamson]

We need to keep track of all the DMA mappings of an iommu container so
that it can be automatically unmapped when the user releases the file
descriptor.  We currently do this using a simple list, where we merge
entries with contiguous iovas and virtual addresses.  Using a tree for
this is a bit more efficient and allows us to use common code instead
of inventing our own.

Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c |  190 ++++++++++++++++++++-------------------
 1 file changed, 96 insertions(+), 94 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 6f3fbc4..0e863b3 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -31,6 +31,7 @@
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/pci.h>		/* pci_bus_type */
+#include <linux/rbtree.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
@@ -50,13 +51,13 @@ MODULE_PARM_DESC(allow_unsafe_interrupts,
 struct vfio_iommu {
 	struct iommu_domain	*domain;
 	struct mutex		lock;
-	struct list_head	dma_list;
+	struct rb_root		dma_list;
 	struct list_head	group_list;
 	bool			cache;
 };
 
 struct vfio_dma {
-	struct list_head	next;
+	struct rb_node		node;
 	dma_addr_t		iova;		/* Device address */
 	unsigned long		vaddr;		/* Process virtual addr */
 	long			npage;		/* Number of pages */
@@ -75,6 +76,49 @@ struct vfio_group {
 
 #define NPAGE_TO_SIZE(npage)	((size_t)(npage) << PAGE_SHIFT)
 
+static struct vfio_dma *vfio_find_dma(struct vfio_iommu *iommu,
+				      dma_addr_t start, size_t size)
+{
+	struct rb_node *node = iommu->dma_list.rb_node;
+
+	while (node) {
+		struct vfio_dma *dma = rb_entry(node, struct vfio_dma, node);
+
+		if (start + size <= dma->iova)
+			node = node->rb_left;
+		else if (start >= dma->iova + NPAGE_TO_SIZE(dma->npage))
+			node = node->rb_right;
+		else
+			return dma;
+	}
+
+	return NULL;
+}
+
+static void vfio_insert_dma(struct vfio_iommu *iommu, struct vfio_dma *new)
+{
+	struct rb_node **link = &iommu->dma_list.rb_node, *parent = NULL;
+	struct vfio_dma *dma;
+
+	while (*link) {
+		parent = *link;
+		dma = rb_entry(parent, struct vfio_dma, node);
+
+		if (new->iova + NPAGE_TO_SIZE(new->npage) <= dma->iova)
+			link = &(*link)->rb_left;
+		else
+			link = &(*link)->rb_right;
+	}
+
+	rb_link_node(&new->node, parent, link);
+	rb_insert_color(&new->node, &iommu->dma_list);
+}
+
+static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
+{
+	rb_erase(&old->node, &iommu->dma_list);
+}
+
 struct vwork {
 	struct mm_struct	*mm;
 	long			npage;
@@ -289,31 +333,8 @@ static int __vfio_dma_map(struct vfio_iommu *iommu, dma_addr_t iova,
 	return 0;
 }
 
-static inline bool ranges_overlap(dma_addr_t start1, size_t size1,
-				  dma_addr_t start2, size_t size2)
-{
-	if (start1 < start2)
-		return (start2 - start1 < size1);
-	else if (start2 < start1)
-		return (start1 - start2 < size2);
-	return (size1 > 0 && size2 > 0);
-}
-
-static struct vfio_dma *vfio_find_dma(struct vfio_iommu *iommu,
-						dma_addr_t start, size_t size)
-{
-	struct vfio_dma *dma;
-
-	list_for_each_entry(dma, &iommu->dma_list, next) {
-		if (ranges_overlap(dma->iova, NPAGE_TO_SIZE(dma->npage),
-				   start, size))
-			return dma;
-	}
-	return NULL;
-}
-
-static long vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
-				    size_t size, struct vfio_dma *dma)
+static int vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
+				   size_t size, struct vfio_dma *dma)
 {
 	struct vfio_dma *split;
 	long npage_lo, npage_hi;
@@ -322,10 +343,9 @@ static long vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
 	if (start <= dma->iova &&
 	    start + size >= dma->iova + NPAGE_TO_SIZE(dma->npage)) {
 		vfio_dma_unmap(iommu, dma->iova, dma->npage, dma->prot);
-		list_del(&dma->next);
-		npage_lo = dma->npage;
+		vfio_remove_dma(iommu, dma);
 		kfree(dma);
-		return npage_lo;
+		return 0;
 	}
 
 	/* Overlap low address of existing range */
@@ -339,7 +359,7 @@ static long vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
 		dma->iova += overlap;
 		dma->vaddr += overlap;
 		dma->npage -= npage_lo;
-		return npage_lo;
+		return 0;
 	}
 
 	/* Overlap high address of existing range */
@@ -351,7 +371,7 @@ static long vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
 
 		vfio_dma_unmap(iommu, start, npage_hi, dma->prot);
 		dma->npage -= npage_hi;
-		return npage_hi;
+		return 0;
 	}
 
 	/* Split existing */
@@ -370,16 +390,16 @@ static long vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
 	split->iova = start + size;
 	split->vaddr = dma->vaddr + NPAGE_TO_SIZE(npage_lo) + size;
 	split->prot = dma->prot;
-	list_add(&split->next, &iommu->dma_list);
-	return size >> PAGE_SHIFT;
+	vfio_insert_dma(iommu, split);
+	return 0;
 }
 
 static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 			     struct vfio_iommu_type1_dma_unmap *unmap)
 {
-	long ret = 0, npage = unmap->size >> PAGE_SHIFT;
-	struct vfio_dma *dma, *tmp;
 	uint64_t mask;
+	struct vfio_dma *dma;
+	int ret = 0;
 
 	mask = ((uint64_t)1 << __ffs(iommu->domain->ops->pgsize_bitmap)) - 1;
 
@@ -393,25 +413,19 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 
 	mutex_lock(&iommu->lock);
 
-	list_for_each_entry_safe(dma, tmp, &iommu->dma_list, next) {
-		if (ranges_overlap(dma->iova, NPAGE_TO_SIZE(dma->npage),
-				   unmap->iova, unmap->size)) {
-			ret = vfio_remove_dma_overlap(iommu, unmap->iova,
-						      unmap->size, dma);
-			if (ret > 0)
-				npage -= ret;
-			if (ret < 0 || npage == 0)
-				break;
-		}
-	}
+	while (!ret && (dma = vfio_find_dma(iommu,
+					    unmap->iova, unmap->size)))
+		ret = vfio_remove_dma_overlap(iommu, unmap->iova,
+					      unmap->size, dma);
+
 	mutex_unlock(&iommu->lock);
-	return ret > 0 ? 0 : (int)ret;
+	return ret;
 }
 
 static int vfio_dma_do_map(struct vfio_iommu *iommu,
 			   struct vfio_iommu_type1_dma_map *map)
 {
-	struct vfio_dma *dma, *pdma = NULL;
+	struct vfio_dma *dma;
 	dma_addr_t iova = map->iova;
 	unsigned long locked, lock_limit, vaddr = map->vaddr;
 	size_t size = map->size;
@@ -452,6 +466,10 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 	if (!npage)
 		return -EINVAL;
 
+	dma = kzalloc(sizeof *dma, GFP_KERNEL);
+	if (!dma)
+		return -ENOMEM;
+
 	mutex_lock(&iommu->lock);
 
 	if (vfio_find_dma(iommu, iova, size)) {
@@ -473,62 +491,45 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 	if (ret)
 		goto out_lock;
 
+	dma->npage = npage;
+	dma->iova = iova;
+	dma->vaddr = vaddr;
+	dma->prot = prot;
+
 	/* Check if we abut a region below - nothing below 0 */
 	if (iova) {
-		dma = vfio_find_dma(iommu, iova - 1, 1);
-		if (dma && dma->prot == prot &&
-		    dma->vaddr + NPAGE_TO_SIZE(dma->npage) == vaddr) {
-
-			dma->npage += npage;
-			iova = dma->iova;
-			vaddr = dma->vaddr;
+		struct vfio_dma *tmp = vfio_find_dma(iommu, iova - 1, 1);
+		if (tmp && tmp->prot == prot &&
+		    tmp->vaddr + NPAGE_TO_SIZE(tmp->npage) == vaddr) {
+			vfio_remove_dma(iommu, tmp);
+			dma->npage += tmp->npage;
+			dma->iova = iova = tmp->iova;
+			dma->vaddr = vaddr = tmp->vaddr;
+			kfree(tmp);
 			npage = dma->npage;
 			size = NPAGE_TO_SIZE(npage);
-
-			pdma = dma;
 		}
 	}
 
 	/* Check if we abut a region above - nothing above ~0 + 1 */
 	if (iova + size) {
-		dma = vfio_find_dma(iommu, iova + size, 1);
-		if (dma && dma->prot == prot &&
-		    dma->vaddr == vaddr + size) {
-
-			dma->npage += npage;
-			dma->iova = iova;
-			dma->vaddr = vaddr;
-
-			/*
-			 * If merged above and below, remove previously
-			 * merged entry.  New entry covers it.
-			 */
-			if (pdma) {
-				list_del(&pdma->next);
-				kfree(pdma);
-			}
-			pdma = dma;
+		struct vfio_dma *tmp = vfio_find_dma(iommu, iova + size, 1);
+		if (tmp && tmp->prot == prot &&
+		    tmp->vaddr == vaddr + size) {
+			vfio_remove_dma(iommu, tmp);
+			dma->npage += tmp->npage;
+			kfree(tmp);
+			npage = dma->npage;
+			size = NPAGE_TO_SIZE(npage);
 		}
 	}
 
-	/* Isolated, new region */
-	if (!pdma) {
-		dma = kzalloc(sizeof *dma, GFP_KERNEL);
-		if (!dma) {
-			ret = -ENOMEM;
-			vfio_dma_unmap(iommu, iova, npage, prot);
-			goto out_lock;
-		}
-
-		dma->npage = npage;
-		dma->iova = iova;
-		dma->vaddr = vaddr;
-		dma->prot = prot;
-		list_add(&dma->next, &iommu->dma_list);
-	}
+	vfio_insert_dma(iommu, dma);
 
 out_lock:
 	mutex_unlock(&iommu->lock);
+	if (ret)
+		kfree(dma);
 	return ret;
 }
 
@@ -606,7 +607,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
 		return ERR_PTR(-ENOMEM);
 
 	INIT_LIST_HEAD(&iommu->group_list);
-	INIT_LIST_HEAD(&iommu->dma_list);
+	iommu->dma_list = RB_ROOT;
 	mutex_init(&iommu->lock);
 
 	/*
@@ -640,7 +641,7 @@ static void vfio_iommu_type1_release(void *iommu_data)
 {
 	struct vfio_iommu *iommu = iommu_data;
 	struct vfio_group *group, *group_tmp;
-	struct vfio_dma *dma, *dma_tmp;
+	struct rb_node *node;
 
 	list_for_each_entry_safe(group, group_tmp, &iommu->group_list, next) {
 		iommu_detach_group(iommu->domain, group->iommu_group);
@@ -648,9 +649,10 @@ static void vfio_iommu_type1_release(void *iommu_data)
 		kfree(group);
 	}
 
-	list_for_each_entry_safe(dma, dma_tmp, &iommu->dma_list, next) {
+	while ((node = rb_first(&iommu->dma_list))) {
+		struct vfio_dma *dma = rb_entry(node, struct vfio_dma, node);
 		vfio_dma_unmap(iommu, dma->iova, dma->npage, dma->prot);
-		list_del(&dma->next);
+		vfio_remove_dma(iommu, dma);
 		kfree(dma);
 	}
 

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