[PATCH v4 0/6] Optimise 64-bit IOVA allocations

[PATCH v4 0/6] Optimise 64-bit IOVA allocations

[Robin Murphy]

v3: https://www.mail-archive.com/iommu@lists.linux-foundation.org/msg19694.html

This was supposed to be just a rebase and repost, but in the meantime I
kept scratching the itch and ended up with two extra patches to simplify
the end result even more - the series was least churny with them added
in the middle, but #5 and #6 remain essentially unchanged from v3, such
that I'm happy the tested-bys all remain valid.

Robin.

Robin Murphy (3):
  iommu/iova: Add rbtree anchor node
  iommu/iova: Simplify cached node logic
  iommu/iova: Extend rbtree node caching

Zhen Lei (3):
  iommu/iova: Optimise rbtree searching
  iommu/iova: Optimise the padding calculation
  iommu/iova: Make dma_32bit_pfn implicit

 drivers/gpu/drm/tegra/drm.c      |   3 +-
 drivers/gpu/host1x/dev.c         |   3 +-
 drivers/iommu/amd_iommu.c        |   7 +-
 drivers/iommu/dma-iommu.c        |  18 +----
 drivers/iommu/intel-iommu.c      |  11 +---
 drivers/iommu/iova.c             | 139 +++++++++++++++++----------------------
 drivers/misc/mic/scif/scif_rma.c |   3 +-
 include/linux/iova.h             |   9 +--
 8 files changed, 74 insertions(+), 119 deletions(-)

-- 
2.13.4.dirty

[PATCH v4 1/6] iommu/iova: Optimise rbtree searching

[Robin Murphy]

From: Zhen Lei <thunder.leizhen@huawei.com>

Checking the IOVA bounds separately before deciding which direction to
continue the search (if necessary) results in redundantly comparing both
pfns twice each. GCC can already determine that the final comparison op
is redundant and optimise it down to 3 in total, but we can go one
further with a little tweak of the ordering (which makes the intent of
the code that much cleaner as a bonus).

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
[rm: rewrote commit message to clarify]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v4: No change

 drivers/iommu/iova.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 33edfa794ae9..f129ff4f5c89 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -342,15 +342,12 @@ private_find_iova(struct iova_domain *iovad, unsigned long pfn)
 	while (node) {
 		struct iova *iova = rb_entry(node, struct iova, node);
 
-		/* If pfn falls within iova's range, return iova */
-		if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
-			return iova;
-		}
-
 		if (pfn < iova->pfn_lo)
 			node = node->rb_left;
-		else if (pfn > iova->pfn_lo)
+		else if (pfn > iova->pfn_hi)
 			node = node->rb_right;
+		else
+			return iova;	/* pfn falls within iova's range */
 	}
 
 	return NULL;
-- 
2.13.4.dirty

[PATCH v4 2/6] iommu/iova: Optimise the padding calculation

[Robin Murphy]

From: Zhen Lei <thunder.leizhen@huawei.com>

The mask for calculating the padding size doesn't change, so there's no
need to recalculate it every loop iteration. Furthermore, Once we've
done that, it becomes clear that we don't actually need to calculate a
padding size at all - by flipping the arithmetic around, we can just
combine the upper limit, size, and mask directly to check against the
lower limit.

For an arm64 build, this alone knocks 20% off the object code size of
the entire alloc_iova() function!

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
[rm: simplified more of the arithmetic, rewrote commit message]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v4:
 - Round align_mask up instead of down (oops!)
 - Remove redundant !curr check
 - Introduce new_pfn variable here to reduce churn in later patches

 drivers/iommu/iova.c | 42 +++++++++++++++---------------------------
 1 file changed, 15 insertions(+), 27 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index f129ff4f5c89..20be9a8b3188 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -182,24 +182,17 @@ iova_insert_rbtree(struct rb_root *root, struct iova *iova,
 	rb_insert_color(&iova->node, root);
 }
 
-/*
- * Computes the padding size required, to make the start address
- * naturally aligned on the power-of-two order of its size
- */
-static unsigned int
-iova_get_pad_size(unsigned int size, unsigned int limit_pfn)
-{
-	return (limit_pfn - size) & (__roundup_pow_of_two(size) - 1);
-}
-
 static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 		unsigned long size, unsigned long limit_pfn,
 			struct iova *new, bool size_aligned)
 {
 	struct rb_node *prev, *curr = NULL;
 	unsigned long flags;
-	unsigned long saved_pfn;
-	unsigned int pad_size = 0;
+	unsigned long saved_pfn, new_pfn;
+	unsigned long align_mask = ~0UL;
+
+	if (size_aligned)
+		align_mask <<= fls_long(size - 1);
 
 	/* Walk the tree backwards */
 	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
@@ -209,31 +202,26 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 	while (curr) {
 		struct iova *curr_iova = rb_entry(curr, struct iova, node);
 
-		if (limit_pfn <= curr_iova->pfn_lo) {
+		if (limit_pfn <= curr_iova->pfn_lo)
 			goto move_left;
-		} else if (limit_pfn > curr_iova->pfn_hi) {
-			if (size_aligned)
-				pad_size = iova_get_pad_size(size, limit_pfn);
-			if ((curr_iova->pfn_hi + size + pad_size) < limit_pfn)
-				break;	/* found a free slot */
-		}
+
+		if (((limit_pfn - size) & align_mask) > curr_iova->pfn_hi)
+			break;	/* found a free slot */
+
 		limit_pfn = curr_iova->pfn_lo;
 move_left:
 		prev = curr;
 		curr = rb_prev(curr);
 	}
 
-	if (!curr) {
-		if (size_aligned)
-			pad_size = iova_get_pad_size(size, limit_pfn);
-		if ((iovad->start_pfn + size + pad_size) > limit_pfn) {
-			spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
-			return -ENOMEM;
-		}
+	new_pfn = (limit_pfn - size) & align_mask;
+	if (limit_pfn < size || new_pfn < iovad->start_pfn) {
+		spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+		return -ENOMEM;
 	}
 
 	/* pfn_lo will point to size aligned address if size_aligned is set */
-	new->pfn_lo = limit_pfn - (size + pad_size);
+	new->pfn_lo = new_pfn;
 	new->pfn_hi = new->pfn_lo + size - 1;
 
 	/* If we have 'prev', it's a valid place to start the insertion. */
-- 
2.13.4.dirty

[PATCH v4 3/6] iommu/iova: Add rbtree anchor node

[Robin Murphy]

Add a permanent dummy IOVA reservation to the rbtree, such that we can
always access the top of the address space instantly. The immediate
benefit is that we remove the overhead of the rb_last() traversal when
not using the cached node, but it also paves the way for further
simplifications.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v4: New

 drivers/iommu/iova.c | 15 +++++++++++++--
 include/linux/iova.h |  1 +
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 20be9a8b3188..03b677afb109 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -24,6 +24,9 @@
 #include <linux/bitops.h>
 #include <linux/cpu.h>
 
+/* The anchor node sits above the top of the usable address space */
+#define IOVA_ANCHOR	~0UL
+
 static bool iova_rcache_insert(struct iova_domain *iovad,
 			       unsigned long pfn,
 			       unsigned long size);
@@ -54,6 +57,9 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 	iovad->dma_32bit_pfn = pfn_32bit + 1;
 	iovad->flush_cb = NULL;
 	iovad->fq = NULL;
+	iovad->anchor.pfn_lo = iovad->anchor.pfn_hi = IOVA_ANCHOR;
+	rb_link_node(&iovad->anchor.node, NULL, &iovad->rbroot.rb_node);
+	rb_insert_color(&iovad->anchor.node, &iovad->rbroot);
 	init_iova_rcaches(iovad);
 }
 EXPORT_SYMBOL_GPL(init_iova_domain);
@@ -112,7 +118,7 @@ __get_cached_rbnode(struct iova_domain *iovad, unsigned long *limit_pfn)
 {
 	if ((*limit_pfn > iovad->dma_32bit_pfn) ||
 		(iovad->cached32_node == NULL))
-		return rb_last(&iovad->rbroot);
+		return rb_prev(&iovad->anchor.node);
 	else {
 		struct rb_node *prev_node = rb_prev(iovad->cached32_node);
 		struct iova *curr_iova =
@@ -246,7 +252,8 @@ EXPORT_SYMBOL(alloc_iova_mem);
 
 void free_iova_mem(struct iova *iova)
 {
-	kmem_cache_free(iova_cache, iova);
+	if (iova->pfn_lo != IOVA_ANCHOR)
+		kmem_cache_free(iova_cache, iova);
 }
 EXPORT_SYMBOL(free_iova_mem);
 
@@ -680,6 +687,10 @@ reserve_iova(struct iova_domain *iovad,
 	struct iova *iova;
 	unsigned int overlap = 0;
 
+	/* Don't allow nonsensical pfns */
+	if (WARN_ON((pfn_hi | pfn_lo) > (ULLONG_MAX >> iova_shift(iovad))))
+		return NULL;
+
 	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
 	for (node = rb_first(&iovad->rbroot); node; node = rb_next(node)) {
 		if (__is_range_overlap(node, pfn_lo, pfn_hi)) {
diff --git a/include/linux/iova.h b/include/linux/iova.h
index d179b9bf7814..22dc30a28387 100644
--- a/include/linux/iova.h
+++ b/include/linux/iova.h
@@ -74,6 +74,7 @@ struct iova_domain {
 	unsigned long	granule;	/* pfn granularity for this domain */
 	unsigned long	start_pfn;	/* Lower limit for this domain */
 	unsigned long	dma_32bit_pfn;
+	struct iova	anchor;		/* rbtree lookup anchor */
 	struct iova_rcache rcaches[IOVA_RANGE_CACHE_MAX_SIZE];	/* IOVA range caches */
 
 	iova_flush_cb	flush_cb;	/* Call-Back function to flush IOMMU
-- 
2.13.4.dirty

[PATCH v4 4/6] iommu/iova: Simplify cached node logic

[Robin Murphy]

The logic of __get_cached_rbnode() is a little obtuse, but then
__get_prev_node_of_cached_rbnode_or_last_node_and_update_limit_pfn()
wouldn't exactly roll off the tongue...

Now that we have the invariant that there is always a valid node to
start searching downwards from, everything gets a bit easier to follow
if we simplify that function to do what it says on the tin and return
the cached node (or anchor node as appropriate) directly. In turn, we
can then deduplicate the rb_prev() and limit_pfn logic into the main
loop itself, further reduce the amount of code under the lock, and
generally make the inner workings a bit less subtle.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v4: New

 drivers/iommu/iova.c | 42 ++++++++++++++----------------------------
 1 file changed, 14 insertions(+), 28 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 03b677afb109..c93a6c46bcb1 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -114,18 +114,12 @@ int init_iova_flush_queue(struct iova_domain *iovad,
 EXPORT_SYMBOL_GPL(init_iova_flush_queue);
 
 static struct rb_node *
-__get_cached_rbnode(struct iova_domain *iovad, unsigned long *limit_pfn)
+__get_cached_rbnode(struct iova_domain *iovad, unsigned long limit_pfn)
 {
-	if ((*limit_pfn > iovad->dma_32bit_pfn) ||
-		(iovad->cached32_node == NULL))
-		return rb_prev(&iovad->anchor.node);
-	else {
-		struct rb_node *prev_node = rb_prev(iovad->cached32_node);
-		struct iova *curr_iova =
-			rb_entry(iovad->cached32_node, struct iova, node);
-		*limit_pfn = curr_iova->pfn_lo;
-		return prev_node;
-	}
+	if (limit_pfn <= iovad->dma_32bit_pfn && iovad->cached32_node)
+		return iovad->cached32_node;
+
+	return &iovad->anchor.node;
 }
 
 static void
@@ -192,7 +186,8 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 		unsigned long size, unsigned long limit_pfn,
 			struct iova *new, bool size_aligned)
 {
-	struct rb_node *prev, *curr = NULL;
+	struct rb_node *curr, *prev;
+	struct iova *curr_iova;
 	unsigned long flags;
 	unsigned long saved_pfn, new_pfn;
 	unsigned long align_mask = ~0UL;
@@ -203,29 +198,20 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 	/* Walk the tree backwards */
 	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
 	saved_pfn = limit_pfn;
-	curr = __get_cached_rbnode(iovad, &limit_pfn);
-	prev = curr;
-	while (curr) {
-		struct iova *curr_iova = rb_entry(curr, struct iova, node);
-
-		if (limit_pfn <= curr_iova->pfn_lo)
-			goto move_left;
-
-		if (((limit_pfn - size) & align_mask) > curr_iova->pfn_hi)
-			break;	/* found a free slot */
-
-		limit_pfn = curr_iova->pfn_lo;
-move_left:
+	curr = __get_cached_rbnode(iovad, limit_pfn);
+	curr_iova = rb_entry(curr, struct iova, node);
+	do {
+		limit_pfn = min(limit_pfn, curr_iova->pfn_lo);
+		new_pfn = (limit_pfn - size) & align_mask;
 		prev = curr;
 		curr = rb_prev(curr);
-	}
+		curr_iova = rb_entry(curr, struct iova, node);
+	} while (curr && new_pfn <= curr_iova->pfn_hi);
 
-	new_pfn = (limit_pfn - size) & align_mask;
 	if (limit_pfn < size || new_pfn < iovad->start_pfn) {
 		spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
 		return -ENOMEM;
 	}
-
 	/* pfn_lo will point to size aligned address if size_aligned is set */
 	new->pfn_lo = new_pfn;
 	new->pfn_hi = new->pfn_lo + size - 1;
-- 
2.13.4.dirty

[PATCH v4 5/6] iommu/iova: Extend rbtree node caching

[Robin Murphy]

The cached node mechanism provides a significant performance benefit for
allocations using a 32-bit DMA mask, but in the case of non-PCI devices
or where the 32-bit space is full, the loss of this benefit can be
significant - on large systems there can be many thousands of entries in
the tree, such that walking all the way down to find free space every
time becomes increasingly awful.

Maintain a similar cached node for the whole IOVA space as a superset of
the 32-bit space so that performance can remain much more consistent.

Inspired by work by Zhen Lei <thunder.leizhen@huawei.com>.

Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v4:
 - Adjust to simplified __get_cached_rbnode() behaviour
 - Cosmetic tweaks

 drivers/iommu/iova.c | 43 +++++++++++++++++++++----------------------
 include/linux/iova.h |  3 ++-
 2 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index c93a6c46bcb1..a125a5786dbf 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -51,6 +51,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 
 	spin_lock_init(&iovad->iova_rbtree_lock);
 	iovad->rbroot = RB_ROOT;
+	iovad->cached_node = NULL;
 	iovad->cached32_node = NULL;
 	iovad->granule = granule;
 	iovad->start_pfn = start_pfn;
@@ -119,39 +120,38 @@ __get_cached_rbnode(struct iova_domain *iovad, unsigned long limit_pfn)
 	if (limit_pfn <= iovad->dma_32bit_pfn && iovad->cached32_node)
 		return iovad->cached32_node;
 
+	if (iovad->cached_node)
+		return iovad->cached_node;
+
 	return &iovad->anchor.node;
 }
 
 static void
-__cached_rbnode_insert_update(struct iova_domain *iovad,
-	unsigned long limit_pfn, struct iova *new)
+__cached_rbnode_insert_update(struct iova_domain *iovad, struct iova *new)
 {
-	if (limit_pfn != iovad->dma_32bit_pfn)
-		return;
-	iovad->cached32_node = &new->node;
+	if (new->pfn_hi < iovad->dma_32bit_pfn)
+		iovad->cached32_node = &new->node;
+	else
+		iovad->cached_node = &new->node;
 }
 
 static void
 __cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
 {
 	struct iova *cached_iova;
-	struct rb_node *curr;
+	struct rb_node **curr;
 
-	if (!iovad->cached32_node)
+	if (free->pfn_hi < iovad->dma_32bit_pfn)
+		curr = &iovad->cached32_node;
+	else
+		curr = &iovad->cached_node;
+
+	if (!*curr)
 		return;
-	curr = iovad->cached32_node;
-	cached_iova = rb_entry(curr, struct iova, node);
 
-	if (free->pfn_lo >= cached_iova->pfn_lo) {
-		struct rb_node *node = rb_next(&free->node);
-		struct iova *iova = rb_entry(node, struct iova, node);
-
-		/* only cache if it's below 32bit pfn */
-		if (node && iova->pfn_lo < iovad->dma_32bit_pfn)
-			iovad->cached32_node = node;
-		else
-			iovad->cached32_node = NULL;
-	}
+	cached_iova = rb_entry(*curr, struct iova, node);
+	if (free->pfn_lo >= cached_iova->pfn_lo)
+		*curr = rb_next(&free->node);
 }
 
 /* Insert the iova into domain rbtree by holding writer lock */
@@ -189,7 +189,7 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 	struct rb_node *curr, *prev;
 	struct iova *curr_iova;
 	unsigned long flags;
-	unsigned long saved_pfn, new_pfn;
+	unsigned long new_pfn;
 	unsigned long align_mask = ~0UL;
 
 	if (size_aligned)
@@ -197,7 +197,6 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 
 	/* Walk the tree backwards */
 	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
-	saved_pfn = limit_pfn;
 	curr = __get_cached_rbnode(iovad, limit_pfn);
 	curr_iova = rb_entry(curr, struct iova, node);
 	do {
@@ -218,7 +217,7 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 
 	/* If we have 'prev', it's a valid place to start the insertion. */
 	iova_insert_rbtree(&iovad->rbroot, new, prev);
-	__cached_rbnode_insert_update(iovad, saved_pfn, new);
+	__cached_rbnode_insert_update(iovad, new);
 
 	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
 
diff --git a/include/linux/iova.h b/include/linux/iova.h
index 22dc30a28387..5eaedf77b152 100644
--- a/include/linux/iova.h
+++ b/include/linux/iova.h
@@ -70,7 +70,8 @@ struct iova_fq {
 struct iova_domain {
 	spinlock_t	iova_rbtree_lock; /* Lock to protect update of rbtree */
 	struct rb_root	rbroot;		/* iova domain rbtree root */
-	struct rb_node	*cached32_node; /* Save last alloced node */
+	struct rb_node	*cached_node;	/* Save last alloced node */
+	struct rb_node	*cached32_node; /* Save last 32-bit alloced node */
 	unsigned long	granule;	/* pfn granularity for this domain */
 	unsigned long	start_pfn;	/* Lower limit for this domain */
 	unsigned long	dma_32bit_pfn;
-- 
2.13.4.dirty

[PATCH v4 6/6] iommu/iova: Make dma_32bit_pfn implicit

[Robin Murphy]

From: Zhen Lei <thunder.leizhen@huawei.com>

Now that the cached node optimisation can apply to all allocations, the
couple of users which were playing tricks with dma_32bit_pfn in order to
benefit from it can stop doing so. Conversely, there is also no need for
all the other users to explicitly calculate a 'real' 32-bit PFN, when
init_iova_domain() can happily do that itself from the page granularity.

CC: Thierry Reding <thierry.reding@gmail.com>
CC: Jonathan Hunter <jonathanh@nvidia.com>
CC: David Airlie <airlied@linux.ie>
CC: Sudeep Dutt <sudeep.dutt@intel.com>
CC: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
[rm: use iova_shift(), rewrote commit message]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v4: No change

 drivers/gpu/drm/tegra/drm.c      |  3 +--
 drivers/gpu/host1x/dev.c         |  3 +--
 drivers/iommu/amd_iommu.c        |  7 ++-----
 drivers/iommu/dma-iommu.c        | 18 +-----------------
 drivers/iommu/intel-iommu.c      | 11 +++--------
 drivers/iommu/iova.c             |  4 ++--
 drivers/misc/mic/scif/scif_rma.c |  3 +--
 include/linux/iova.h             |  5 ++---
 8 files changed, 13 insertions(+), 41 deletions(-)

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 597d563d636a..b822e484b7e5 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -155,8 +155,7 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
 
 		order = __ffs(tegra->domain->pgsize_bitmap);
 		init_iova_domain(&tegra->carveout.domain, 1UL << order,
-				 carveout_start >> order,
-				 carveout_end >> order);
+				 carveout_start >> order);
 
 		tegra->carveout.shift = iova_shift(&tegra->carveout.domain);
 		tegra->carveout.limit = carveout_end >> tegra->carveout.shift;
diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c
index 7f22c5c37660..5267c62e8896 100644
--- a/drivers/gpu/host1x/dev.c
+++ b/drivers/gpu/host1x/dev.c
@@ -198,8 +198,7 @@ static int host1x_probe(struct platform_device *pdev)
 
 		order = __ffs(host->domain->pgsize_bitmap);
 		init_iova_domain(&host->iova, 1UL << order,
-				 geometry->aperture_start >> order,
-				 geometry->aperture_end >> order);
+				 geometry->aperture_start >> order);
 		host->iova_end = geometry->aperture_end;
 	}
 
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 51f8215877f5..647ab7691aee 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -63,7 +63,6 @@
 /* IO virtual address start page frame number */
 #define IOVA_START_PFN		(1)
 #define IOVA_PFN(addr)		((addr) >> PAGE_SHIFT)
-#define DMA_32BIT_PFN		IOVA_PFN(DMA_BIT_MASK(32))
 
 /* Reserved IOVA ranges */
 #define MSI_RANGE_START		(0xfee00000)
@@ -1788,8 +1787,7 @@ static struct dma_ops_domain *dma_ops_domain_alloc(void)
 	if (!dma_dom->domain.pt_root)
 		goto free_dma_dom;
 
-	init_iova_domain(&dma_dom->iovad, PAGE_SIZE,
-			 IOVA_START_PFN, DMA_32BIT_PFN);
+	init_iova_domain(&dma_dom->iovad, PAGE_SIZE, IOVA_START_PFN);
 
 	if (init_iova_flush_queue(&dma_dom->iovad, iova_domain_flush_tlb, NULL))
 		goto free_dma_dom;
@@ -2696,8 +2694,7 @@ static int init_reserved_iova_ranges(void)
 	struct pci_dev *pdev = NULL;
 	struct iova *val;
 
-	init_iova_domain(&reserved_iova_ranges, PAGE_SIZE,
-			 IOVA_START_PFN, DMA_32BIT_PFN);
+	init_iova_domain(&reserved_iova_ranges, PAGE_SIZE, IOVA_START_PFN);
 
 	lockdep_set_class(&reserved_iova_ranges.iova_rbtree_lock,
 			  &reserved_rbtree_key);
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 9d1cebe7f6cb..191be9c80a8a 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -292,18 +292,7 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
 		/* ...then finally give it a kicking to make sure it fits */
 		base_pfn = max_t(unsigned long, base_pfn,
 				domain->geometry.aperture_start >> order);
-		end_pfn = min_t(unsigned long, end_pfn,
-				domain->geometry.aperture_end >> order);
 	}
-	/*
-	 * PCI devices may have larger DMA masks, but still prefer allocating
-	 * within a 32-bit mask to avoid DAC addressing. Such limitations don't
-	 * apply to the typical platform device, so for those we may as well
-	 * leave the cache limit at the top of their range to save an rb_last()
-	 * traversal on every allocation.
-	 */
-	if (dev && dev_is_pci(dev))
-		end_pfn &= DMA_BIT_MASK(32) >> order;
 
 	/* start_pfn is always nonzero for an already-initialised domain */
 	if (iovad->start_pfn) {
@@ -312,16 +301,11 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
 			pr_warn("Incompatible range for DMA domain\n");
 			return -EFAULT;
 		}
-		/*
-		 * If we have devices with different DMA masks, move the free
-		 * area cache limit down for the benefit of the smaller one.
-		 */
-		iovad->dma_32bit_pfn = min(end_pfn + 1, iovad->dma_32bit_pfn);
 
 		return 0;
 	}
 
-	init_iova_domain(iovad, 1UL << order, base_pfn, end_pfn);
+	init_iova_domain(iovad, 1UL << order, base_pfn);
 	if (!dev)
 		return 0;
 
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 6784a05dd6b2..ebb48353dd39 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -82,8 +82,6 @@
 #define IOVA_START_PFN		(1)
 
 #define IOVA_PFN(addr)		((addr) >> PAGE_SHIFT)
-#define DMA_32BIT_PFN		IOVA_PFN(DMA_BIT_MASK(32))
-#define DMA_64BIT_PFN		IOVA_PFN(DMA_BIT_MASK(64))
 
 /* page table handling */
 #define LEVEL_STRIDE		(9)
@@ -1878,8 +1876,7 @@ static int dmar_init_reserved_ranges(void)
 	struct iova *iova;
 	int i;
 
-	init_iova_domain(&reserved_iova_list, VTD_PAGE_SIZE, IOVA_START_PFN,
-			DMA_32BIT_PFN);
+	init_iova_domain(&reserved_iova_list, VTD_PAGE_SIZE, IOVA_START_PFN);
 
 	lockdep_set_class(&reserved_iova_list.iova_rbtree_lock,
 		&reserved_rbtree_key);
@@ -1938,8 +1935,7 @@ static int domain_init(struct dmar_domain *domain, struct intel_iommu *iommu,
 	unsigned long sagaw;
 	int err;
 
-	init_iova_domain(&domain->iovad, VTD_PAGE_SIZE, IOVA_START_PFN,
-			DMA_32BIT_PFN);
+	init_iova_domain(&domain->iovad, VTD_PAGE_SIZE, IOVA_START_PFN);
 
 	err = init_iova_flush_queue(&domain->iovad,
 				    iommu_flush_iova, iova_entry_free);
@@ -4897,8 +4893,7 @@ static int md_domain_init(struct dmar_domain *domain, int guest_width)
 {
 	int adjust_width;
 
-	init_iova_domain(&domain->iovad, VTD_PAGE_SIZE, IOVA_START_PFN,
-			DMA_32BIT_PFN);
+	init_iova_domain(&domain->iovad, VTD_PAGE_SIZE, IOVA_START_PFN);
 	domain_reserve_special_ranges(domain);
 
 	/* calculate AGAW */
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index a125a5786dbf..dbe26067250e 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -40,7 +40,7 @@ static void fq_flush_timeout(unsigned long data);
 
 void
 init_iova_domain(struct iova_domain *iovad, unsigned long granule,
-	unsigned long start_pfn, unsigned long pfn_32bit)
+	unsigned long start_pfn)
 {
 	/*
 	 * IOVA granularity will normally be equal to the smallest
@@ -55,7 +55,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 	iovad->cached32_node = NULL;
 	iovad->granule = granule;
 	iovad->start_pfn = start_pfn;
-	iovad->dma_32bit_pfn = pfn_32bit + 1;
+	iovad->dma_32bit_pfn = 1UL << (32 - iova_shift(iovad));
 	iovad->flush_cb = NULL;
 	iovad->fq = NULL;
 	iovad->anchor.pfn_lo = iovad->anchor.pfn_hi = IOVA_ANCHOR;
diff --git a/drivers/misc/mic/scif/scif_rma.c b/drivers/misc/mic/scif/scif_rma.c
index 329727e00e97..c824329f7012 100644
--- a/drivers/misc/mic/scif/scif_rma.c
+++ b/drivers/misc/mic/scif/scif_rma.c
@@ -39,8 +39,7 @@ void scif_rma_ep_init(struct scif_endpt *ep)
 	struct scif_endpt_rma_info *rma = &ep->rma_info;
 
 	mutex_init(&rma->rma_lock);
-	init_iova_domain(&rma->iovad, PAGE_SIZE, SCIF_IOVA_START_PFN,
-			 SCIF_DMA_64BIT_PFN);
+	init_iova_domain(&rma->iovad, PAGE_SIZE, SCIF_IOVA_START_PFN);
 	spin_lock_init(&rma->tc_lock);
 	mutex_init(&rma->mmn_lock);
 	INIT_LIST_HEAD(&rma->reg_list);
diff --git a/include/linux/iova.h b/include/linux/iova.h
index 5eaedf77b152..c696ee81054e 100644
--- a/include/linux/iova.h
+++ b/include/linux/iova.h
@@ -155,7 +155,7 @@ struct iova *reserve_iova(struct iova_domain *iovad, unsigned long pfn_lo,
 	unsigned long pfn_hi);
 void copy_reserved_iova(struct iova_domain *from, struct iova_domain *to);
 void init_iova_domain(struct iova_domain *iovad, unsigned long granule,
-	unsigned long start_pfn, unsigned long pfn_32bit);
+	unsigned long start_pfn);
 int init_iova_flush_queue(struct iova_domain *iovad,
 			  iova_flush_cb flush_cb, iova_entry_dtor entry_dtor);
 struct iova *find_iova(struct iova_domain *iovad, unsigned long pfn);
@@ -231,8 +231,7 @@ static inline void copy_reserved_iova(struct iova_domain *from,
 
 static inline void init_iova_domain(struct iova_domain *iovad,
 				    unsigned long granule,
-				    unsigned long start_pfn,
-				    unsigned long pfn_32bit)
+				    unsigned long start_pfn)
 {
 }
 
-- 
2.13.4.dirty

[PATCH v4 7/6] iommu/iova: Make cached_node always valid

[Robin Murphy]

With the anchor node at the top of the rbtree, there is always a valid
node for rb_next() to return, such that cached_node is only ever NULL
until the first allocation. Initialising it to point at the anchor node
gets rid of that window and makes the NULL checking entirely redundant.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

Oops, spotted this one slightly too late. This could be squashed into
patch #5 (which I'll do myself if I there's any cause to resend the
whole series again).

Robin.

 drivers/iommu/iova.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index a7af8273fa98..ec443c0a8319 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -51,7 +51,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 
 	spin_lock_init(&iovad->iova_rbtree_lock);
 	iovad->rbroot = RB_ROOT;
-	iovad->cached_node = NULL;
+	iovad->cached_node = &iovad->anchor.node;
 	iovad->cached32_node = NULL;
 	iovad->granule = granule;
 	iovad->start_pfn = start_pfn;
@@ -120,10 +120,7 @@ __get_cached_rbnode(struct iova_domain *iovad, unsigned long limit_pfn)
 	if (limit_pfn <= iovad->dma_32bit_pfn && iovad->cached32_node)
 		return iovad->cached32_node;
 
-	if (iovad->cached_node)
-		return iovad->cached_node;
-
-	return &iovad->anchor.node;
+	return iovad->cached_node;
 }
 
 static void
@@ -141,14 +138,11 @@ __cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
 	struct iova *cached_iova;
 	struct rb_node **curr;
 
-	if (free->pfn_hi < iovad->dma_32bit_pfn)
+	if (free->pfn_hi < iovad->dma_32bit_pfn && iovad->cached32_node)
 		curr = &iovad->cached32_node;
 	else
 		curr = &iovad->cached_node;
 
-	if (!*curr)
-		return;
-
 	cached_iova = rb_entry(*curr, struct iova, node);
 	if (free->pfn_lo >= cached_iova->pfn_lo)
 		*curr = rb_next(&free->node);
-- 
2.13.4.dirty

[PATCH v4 7/6] iommu/iova: Make cached_node always valid

[Robin Murphy]

With the anchor node at the top of the rbtree, there is always a valid
node for rb_next() to return, such that cached_node is only ever NULL
until the first allocation. Initialising it to point at the anchor node
gets rid of that window and makes the NULL checking entirely redundant.

Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
---

Oops, spotted this one slightly too late. This could be squashed into
patch #5 (which I'll do myself if I there's any cause to resend the
whole series again).

Robin.

 drivers/iommu/iova.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index a7af8273fa98..ec443c0a8319 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -51,7 +51,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 
 	spin_lock_init(&iovad->iova_rbtree_lock);
 	iovad->rbroot = RB_ROOT;
-	iovad->cached_node = NULL;
+	iovad->cached_node = &iovad->anchor.node;
 	iovad->cached32_node = NULL;
 	iovad->granule = granule;
 	iovad->start_pfn = start_pfn;
@@ -120,10 +120,7 @@ __get_cached_rbnode(struct iova_domain *iovad, unsigned long limit_pfn)
 	if (limit_pfn <= iovad->dma_32bit_pfn && iovad->cached32_node)
 		return iovad->cached32_node;
 
-	if (iovad->cached_node)
-		return iovad->cached_node;
-
-	return &iovad->anchor.node;
+	return iovad->cached_node;
 }
 
 static void
@@ -141,14 +138,11 @@ __cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
 	struct iova *cached_iova;
 	struct rb_node **curr;
 
-	if (free->pfn_hi < iovad->dma_32bit_pfn)
+	if (free->pfn_hi < iovad->dma_32bit_pfn && iovad->cached32_node)
 		curr = &iovad->cached32_node;
 	else
 		curr = &iovad->cached_node;
 
-	if (!*curr)
-		return;
-
 	cached_iova = rb_entry(*curr, struct iova, node);
 	if (free->pfn_lo >= cached_iova->pfn_lo)
 		*curr = rb_next(&free->node);
-- 
2.13.4.dirty

Re: [PATCH v4 5/6] iommu/iova: Extend rbtree node caching

[Tomasz Nowicki]

Hi Robin,

On 19.09.2017 18:31, Robin Murphy wrote:
> The cached node mechanism provides a significant performance benefit for
> allocations using a 32-bit DMA mask, but in the case of non-PCI devices
> or where the 32-bit space is full, the loss of this benefit can be
> significant - on large systems there can be many thousands of entries in
> the tree, such that walking all the way down to find free space every
> time becomes increasingly awful.
> 
> Maintain a similar cached node for the whole IOVA space as a superset of
> the 32-bit space so that performance can remain much more consistent.
> 
> Inspired by work by Zhen Lei <thunder.leizhen@huawei.com>.
> 
> Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
> Tested-by: Nate Watterson <nwatters@codeaurora.org>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> 
> v4:
>   - Adjust to simplified __get_cached_rbnode() behaviour
>   - Cosmetic tweaks
> 
>   drivers/iommu/iova.c | 43 +++++++++++++++++++++----------------------
>   include/linux/iova.h |  3 ++-
>   2 files changed, 23 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index c93a6c46bcb1..a125a5786dbf 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -51,6 +51,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
>   
>   	spin_lock_init(&iovad->iova_rbtree_lock);
>   	iovad->rbroot = RB_ROOT;
> +	iovad->cached_node = NULL;
>   	iovad->cached32_node = NULL;
>   	iovad->granule = granule;
>   	iovad->start_pfn = start_pfn;
> @@ -119,39 +120,38 @@ __get_cached_rbnode(struct iova_domain *iovad, unsigned long limit_pfn)
>   	if (limit_pfn <= iovad->dma_32bit_pfn && iovad->cached32_node)
>   		return iovad->cached32_node;
>   
> +	if (iovad->cached_node)
> +		return iovad->cached_node;
> +
>   	return &iovad->anchor.node;
>   }
>   
>   static void
> -__cached_rbnode_insert_update(struct iova_domain *iovad,
> -	unsigned long limit_pfn, struct iova *new)
> +__cached_rbnode_insert_update(struct iova_domain *iovad, struct iova *new)
>   {
> -	if (limit_pfn != iovad->dma_32bit_pfn)
> -		return;
> -	iovad->cached32_node = &new->node;
> +	if (new->pfn_hi < iovad->dma_32bit_pfn)
> +		iovad->cached32_node = &new->node;
> +	else
> +		iovad->cached_node = &new->node;
>   }
>   
>   static void
>   __cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
>   {
>   	struct iova *cached_iova;
> -	struct rb_node *curr;
> +	struct rb_node **curr;
>   
> -	if (!iovad->cached32_node)
> +	if (free->pfn_hi < iovad->dma_32bit_pfn)
> +		curr = &iovad->cached32_node;
> +	else
> +		curr = &iovad->cached_node;
> +
> +	if (!*curr)
>   		return;
> -	curr = iovad->cached32_node;
> -	cached_iova = rb_entry(curr, struct iova, node);
>   
> -	if (free->pfn_lo >= cached_iova->pfn_lo) {
> -		struct rb_node *node = rb_next(&free->node);
> -		struct iova *iova = rb_entry(node, struct iova, node);
> -
> -		/* only cache if it's below 32bit pfn */
> -		if (node && iova->pfn_lo < iovad->dma_32bit_pfn)
> -			iovad->cached32_node = node;
> -		else
> -			iovad->cached32_node = NULL;
> -	}
> +	cached_iova = rb_entry(*curr, struct iova, node);
> +	if (free->pfn_lo >= cached_iova->pfn_lo)
> +		*curr = rb_next(&free->node);

IMO, we may incorrectly update iovad->cached32_node here.

                               32-bit boundary
      --------       --------        |          --------       --------
     |        |     |        |       |         |        |     |        |
----  IOVA0   -----  IOVA1   -----------------  IOVA3   -----  anchor |
     |        |     |        |       |         |        |     |        |
      --------       --------        |          --------       --------

If we free last IOVA from 32-bit space (IOVA1) we will update 
iovad->cached32_node to IOVA3.

Thanks,
Tomasz

Re: [PATCH v4 5/6] iommu/iova: Extend rbtree node caching

[Robin Murphy]

On 20/09/17 13:59, Tomasz Nowicki wrote:
> Hi Robin,
> 
> On 19.09.2017 18:31, Robin Murphy wrote:
>> The cached node mechanism provides a significant performance benefit for
>> allocations using a 32-bit DMA mask, but in the case of non-PCI devices
>> or where the 32-bit space is full, the loss of this benefit can be
>> significant - on large systems there can be many thousands of entries in
>> the tree, such that walking all the way down to find free space every
>> time becomes increasingly awful.
>>
>> Maintain a similar cached node for the whole IOVA space as a superset of
>> the 32-bit space so that performance can remain much more consistent.
>>
>> Inspired by work by Zhen Lei <thunder.leizhen@huawei.com>.
>>
>> Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
>> Tested-by: Nate Watterson <nwatters@codeaurora.org>
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
>> ---
>>
>> v4:
>>   - Adjust to simplified __get_cached_rbnode() behaviour
>>   - Cosmetic tweaks
>>
>>   drivers/iommu/iova.c | 43 +++++++++++++++++++++----------------------
>>   include/linux/iova.h |  3 ++-
>>   2 files changed, 23 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
>> index c93a6c46bcb1..a125a5786dbf 100644
>> --- a/drivers/iommu/iova.c
>> +++ b/drivers/iommu/iova.c
>> @@ -51,6 +51,7 @@ init_iova_domain(struct iova_domain *iovad, unsigned
>> long granule,
>>         spin_lock_init(&iovad->iova_rbtree_lock);
>>       iovad->rbroot = RB_ROOT;
>> +    iovad->cached_node = NULL;
>>       iovad->cached32_node = NULL;
>>       iovad->granule = granule;
>>       iovad->start_pfn = start_pfn;
>> @@ -119,39 +120,38 @@ __get_cached_rbnode(struct iova_domain *iovad,
>> unsigned long limit_pfn)
>>       if (limit_pfn <= iovad->dma_32bit_pfn && iovad->cached32_node)
>>           return iovad->cached32_node;
>>   +    if (iovad->cached_node)
>> +        return iovad->cached_node;
>> +
>>       return &iovad->anchor.node;
>>   }
>>     static void
>> -__cached_rbnode_insert_update(struct iova_domain *iovad,
>> -    unsigned long limit_pfn, struct iova *new)
>> +__cached_rbnode_insert_update(struct iova_domain *iovad, struct iova
>> *new)
>>   {
>> -    if (limit_pfn != iovad->dma_32bit_pfn)
>> -        return;
>> -    iovad->cached32_node = &new->node;
>> +    if (new->pfn_hi < iovad->dma_32bit_pfn)
>> +        iovad->cached32_node = &new->node;
>> +    else
>> +        iovad->cached_node = &new->node;
>>   }
>>     static void
>>   __cached_rbnode_delete_update(struct iova_domain *iovad, struct iova
>> *free)
>>   {
>>       struct iova *cached_iova;
>> -    struct rb_node *curr;
>> +    struct rb_node **curr;
>>   -    if (!iovad->cached32_node)
>> +    if (free->pfn_hi < iovad->dma_32bit_pfn)
>> +        curr = &iovad->cached32_node;
>> +    else
>> +        curr = &iovad->cached_node;
>> +
>> +    if (!*curr)
>>           return;
>> -    curr = iovad->cached32_node;
>> -    cached_iova = rb_entry(curr, struct iova, node);
>>   -    if (free->pfn_lo >= cached_iova->pfn_lo) {
>> -        struct rb_node *node = rb_next(&free->node);
>> -        struct iova *iova = rb_entry(node, struct iova, node);
>> -
>> -        /* only cache if it's below 32bit pfn */
>> -        if (node && iova->pfn_lo < iovad->dma_32bit_pfn)
>> -            iovad->cached32_node = node;
>> -        else
>> -            iovad->cached32_node = NULL;
>> -    }
>> +    cached_iova = rb_entry(*curr, struct iova, node);
>> +    if (free->pfn_lo >= cached_iova->pfn_lo)
>> +        *curr = rb_next(&free->node);
> 
> IMO, we may incorrectly update iovad->cached32_node here.
> 
>                               32-bit boundary
>      --------       --------        |          --------       --------
>     |        |     |        |       |         |        |     |        |
> ----  IOVA0   -----  IOVA1   -----------------  IOVA3   -----  anchor |
>     |        |     |        |       |         |        |     |        |
>      --------       --------        |          --------       --------
> 
> If we free last IOVA from 32-bit space (IOVA1) we will update
> iovad->cached32_node to IOVA3.

That in itself is intentional and correct - the cached node is where we
*start* searching for free space, so if the topmost 32-bit pfn is free,
we want to start from whichever node represents the next-highest pfn.
Even if more 64-bit IOVAs were allocated below IOVA3 before the next
32-bit allocation, walking through those is better that walking all the
way down from the anchor.

However, you have made me realise that if IOVA3 were freed before the
next 32-bit allocation things we'd only update cached_node and leave
cached32_node with a stale pointer...

I'll get a v5 out tomorrow (and keep the new stuff at the end of the
series this time)

Thanks,
Robin.