[PATCH 2/2] iommu: Introduce Interface for IOMMU TLB Flushing

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

From: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>

With the current IOMMU-API the hardware TLBs have to be
flushed in every iommu_ops->unmap() call-back.

For unmapping large amounts of address space, like it
happens when a KVM domain with assigned devices is
destroyed, this causes thousands of unnecessary TLB flushes
in the IOMMU hardware because the unmap call-back runs for
every unmapped physical page.

With the TLB Flush Interface and the new iommu_unmap_fast()
function introduced here the need to clean the hardware TLBs
is removed from the unmapping code-path. Users of
iommu_unmap_fast() have to explicitly call the TLB-Flush
functions to sync the page-table changes to the hardware.

Three functions for TLB-Flushes are introduced:

	* iommu_flush_tlb_all() - Flushes all TLB entries
	                          associated with that
				  domain. TLBs entries are
				  flushed when this function
				  returns.

	* iommu_tlb_range_add() - This will add a given
				  range to the flush queue
				  for this domain.

	* iommu_tlb_sync() - Flushes all queued ranges from
			     the hardware TLBs. Returns when
			     the flush is finished.

The semantic of this interface is intentionally similar to
the iommu_gather_ops from the io-pgtable code.

Cc: Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Cc: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
Signed-off-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
---
 drivers/iommu/iommu.c | 32 ++++++++++++++++++++---
 include/linux/iommu.h | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 99 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3f6ea16..0f68342 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -527,6 +527,8 @@ static int iommu_group_create_direct_mappings(struct iommu_group *group,
 
 	}
 
+	iommu_flush_tlb_all(domain);
+
 out:
 	iommu_put_resv_regions(dev, &mappings);
 
@@ -1556,13 +1558,16 @@ int iommu_map(struct iommu_domain *domain, unsigned long iova,
 }
 EXPORT_SYMBOL_GPL(iommu_map);
 
-size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova, size_t size)
+static size_t __iommu_unmap(struct iommu_domain *domain,
+			    unsigned long iova, size_t size,
+			    bool sync)
 {
+	const struct iommu_ops *ops = domain->ops;
 	size_t unmapped_page, unmapped = 0;
-	unsigned int min_pagesz;
 	unsigned long orig_iova = iova;
+	unsigned int min_pagesz;
 
-	if (unlikely(domain->ops->unmap == NULL ||
+	if (unlikely(ops->unmap == NULL ||
 		     domain->pgsize_bitmap == 0UL))
 		return -ENODEV;
 
@@ -1592,10 +1597,13 @@ size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova, size_t size)
 	while (unmapped < size) {
 		size_t pgsize = iommu_pgsize(domain, iova, size - unmapped);
 
-		unmapped_page = domain->ops->unmap(domain, iova, pgsize);
+		unmapped_page = ops->unmap(domain, iova, pgsize);
 		if (!unmapped_page)
 			break;
 
+		if (sync && ops->iotlb_range_add)
+			ops->iotlb_range_add(domain, iova, pgsize);
+
 		pr_debug("unmapped: iova 0x%lx size 0x%zx\n",
 			 iova, unmapped_page);
 
@@ -1603,11 +1611,27 @@ size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova, size_t size)
 		unmapped += unmapped_page;
 	}
 
+	if (sync && ops->iotlb_sync)
+		ops->iotlb_sync(domain);
+
 	trace_unmap(orig_iova, size, unmapped);
 	return unmapped;
 }
+
+size_t iommu_unmap(struct iommu_domain *domain,
+		   unsigned long iova, size_t size)
+{
+	return __iommu_unmap(domain, iova, size, true);
+}
 EXPORT_SYMBOL_GPL(iommu_unmap);
 
+size_t iommu_unmap_fast(struct iommu_domain *domain,
+			unsigned long iova, size_t size)
+{
+	return __iommu_unmap(domain, iova, size, false);
+}
+EXPORT_SYMBOL_GPL(iommu_unmap_fast);
+
 size_t default_iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
 			 struct scatterlist *sg, unsigned int nents, int prot)
 {
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 2cb54ad..67fa954 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -167,6 +167,10 @@ struct iommu_resv_region {
  * @map: map a physically contiguous memory region to an iommu domain
  * @unmap: unmap a physically contiguous memory region from an iommu domain
  * @map_sg: map a scatter-gather list of physically contiguous memory chunks
+ * @flush_tlb_all: Synchronously flush all hardware TLBs for this domain
+ * @tlb_range_add: Add a given iova range to the flush queue for this domain
+ * @tlb_sync: Flush all queued ranges from the hardware TLBs and empty flush
+ *            queue
  * to an iommu domain
  * @iova_to_phys: translate iova to physical address
  * @add_device: add device to iommu grouping
@@ -199,6 +203,10 @@ struct iommu_ops {
 		     size_t size);
 	size_t (*map_sg)(struct iommu_domain *domain, unsigned long iova,
 			 struct scatterlist *sg, unsigned int nents, int prot);
+	void (*flush_iotlb_all)(struct iommu_domain *domain);
+	void (*iotlb_range_add)(struct iommu_domain *domain,
+				unsigned long iova, size_t size);
+	void (*iotlb_sync)(struct iommu_domain *domain);
 	phys_addr_t (*iova_to_phys)(struct iommu_domain *domain, dma_addr_t iova);
 	int (*add_device)(struct device *dev);
 	void (*remove_device)(struct device *dev);
@@ -286,7 +294,9 @@ extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev);
 extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
 		     phys_addr_t paddr, size_t size, int prot);
 extern size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova,
-		       size_t size);
+			  size_t size);
+extern size_t iommu_unmap_fast(struct iommu_domain *domain,
+			       unsigned long iova, size_t size);
 extern size_t default_iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
 				struct scatterlist *sg,unsigned int nents,
 				int prot);
@@ -343,6 +353,25 @@ extern void iommu_domain_window_disable(struct iommu_domain *domain, u32 wnd_nr)
 extern int report_iommu_fault(struct iommu_domain *domain, struct device *dev,
 			      unsigned long iova, int flags);
 
+static inline void iommu_flush_tlb_all(struct iommu_domain *domain)
+{
+	if (domain->ops->flush_iotlb_all)
+		domain->ops->flush_iotlb_all(domain);
+}
+
+static inline void iommu_tlb_range_add(struct iommu_domain *domain,
+				       unsigned long iova, size_t size)
+{
+	if (domain->ops->iotlb_range_add)
+		domain->ops->iotlb_range_add(domain, iova, size);
+}
+
+static inline void iommu_tlb_sync(struct iommu_domain *domain)
+{
+	if (domain->ops->iotlb_sync)
+		domain->ops->iotlb_sync(domain);
+}
+
 static inline size_t iommu_map_sg(struct iommu_domain *domain,
 				  unsigned long iova, struct scatterlist *sg,
 				  unsigned int nents, int prot)
@@ -350,6 +379,20 @@ static inline size_t iommu_map_sg(struct iommu_domain *domain,
 	return domain->ops->map_sg(domain, iova, sg, nents, prot);
 }
 
+static inline size_t iommu_map_sg_sync(struct iommu_domain *domain,
+				       unsigned long iova,
+				       struct scatterlist *sg,
+				       unsigned int nents, int prot)
+{
+	size_t size = domain->ops->map_sg(domain, iova, sg, nents, prot);
+	if (size > 0) {
+		iommu_tlb_range_add(domain, iova, size);
+		iommu_tlb_sync(domain);
+	}
+
+	return size;
+}
+
 /* PCI device grouping function */
 extern struct iommu_group *pci_device_group(struct device *dev);
 /* Generic device grouping function */
@@ -436,6 +479,12 @@ static inline int iommu_unmap(struct iommu_domain *domain, unsigned long iova,
 	return -ENODEV;
 }
 
+static inline int iommu_unmap_fast(struct iommu_domain *domain, unsigned long iova,
+				   int gfp_order)
+{
+	return -ENODEV;
+}
+
 static inline size_t iommu_map_sg(struct iommu_domain *domain,
 				  unsigned long iova, struct scatterlist *sg,
 				  unsigned int nents, int prot)
@@ -443,6 +492,27 @@ static inline size_t iommu_map_sg(struct iommu_domain *domain,
 	return -ENODEV;
 }
 
+static inline size_t iommu_map_sg_sync(struct iommu_domain *domain,
+				       unsigned long iova,
+				       struct scatterlist *sg,
+				       unsigned int nents, int prot)
+{
+	return -ENODEV;
+}
+
+static inline void iommu_flush_tlb_all(struct iommu_domain *domain)
+{
+}
+
+static inline void iommu_tlb_range_add(struct iommu_domain *domain,
+				       unsigned long iova, size_t size)
+{
+}
+
+static inline void iommu_tlb_sync(struct iommu_domain *domain)
+{
+}
+
 static inline int iommu_domain_window_enable(struct iommu_domain *domain,
 					     u32 wnd_nr, phys_addr_t paddr,
 					     u64 size, int prot)
-- 
2.7.4