[Xen-devel] [PATCH v6 18/19] swiotlb-xen: introduce a rbtree to track phys to bus mappings

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Introduce a second red-back tree to track phys to bus mappings created after
the initialization of the swiotlb buffer.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 drivers/xen/swiotlb-xen.c |   99 +++++++++++++++++++++++++++++++++++++-------
 1 files changed, 83 insertions(+), 16 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 3011736..022bcaf 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -79,7 +79,8 @@ struct xen_dma_info {
        dma_addr_t dma_addr;
        phys_addr_t phys_addr;
        size_t size;
-       struct rb_node rbnode;
+       struct rb_node rbnode_dma;
+       struct rb_node rbnode_phys;
 };
 
 /*
@@ -96,8 +97,13 @@ static struct xen_dma_info *xen_dma_seg;
  * mappings.
  */
 static struct rb_root bus_to_phys = RB_ROOT;
+/*
+ * This tree keeps track of physical address to bus address
+ * mappings apart from the ones belonging to the initial swiotlb buffer.
+ */
+static struct rb_root phys_to_bus = RB_ROOT;
 
-static int xen_dma_add_entry(struct xen_dma_info *new)
+static int xen_dma_add_entry_bus(struct xen_dma_info *new)
 {
        struct rb_node **link = &bus_to_phys.rb_node;
        struct rb_node *parent = NULL;
@@ -106,7 +112,7 @@ static int xen_dma_add_entry(struct xen_dma_info *new)
 
        while (*link) {
                parent = *link;
-               entry = rb_entry(parent, struct xen_dma_info, rbnode);
+               entry = rb_entry(parent, struct xen_dma_info, rbnode_dma);
 
                if (new->dma_addr == entry->dma_addr)
                        goto err_out;
@@ -118,8 +124,41 @@ static int xen_dma_add_entry(struct xen_dma_info *new)
                else
                        link = &(*link)->rb_right;
        }
-       rb_link_node(&new->rbnode, parent, link);
-       rb_insert_color(&new->rbnode, &bus_to_phys);
+       rb_link_node(&new->rbnode_dma, parent, link);
+       rb_insert_color(&new->rbnode_dma, &bus_to_phys);
+       goto out;
+
+err_out:
+       rc = -EINVAL;
+       pr_warn("%s: cannot add phys=%pa -> dma=%pa: phys=%pa -> dma=%pa 
already exists\n",
+                       __func__, &new->phys_addr, &new->dma_addr, 
&entry->phys_addr, &entry->dma_addr);
+out:
+       return rc;
+}
+
+static int xen_dma_add_entry_phys(struct xen_dma_info *new)
+{
+       struct rb_node **link = &phys_to_bus.rb_node;
+       struct rb_node *parent = NULL;
+       struct xen_dma_info *entry;
+       int rc = 0;
+
+       while (*link) {
+               parent = *link;
+               entry = rb_entry(parent, struct xen_dma_info, rbnode_phys);
+
+               if (new->dma_addr == entry->dma_addr)
+                       goto err_out;
+               if (new->phys_addr == entry->phys_addr)
+                       goto err_out;
+
+               if (new->phys_addr < entry->phys_addr)
+                       link = &(*link)->rb_left;
+               else
+                       link = &(*link)->rb_right;
+       }
+       rb_link_node(&new->rbnode_phys, parent, link);
+       rb_insert_color(&new->rbnode_phys, &phys_to_bus);
        goto out;
 
 err_out:
@@ -130,13 +169,22 @@ out:
        return rc;
 }
 
+static int xen_dma_add_entry(struct xen_dma_info *new)
+{
+       int rc;
+       if ((rc = xen_dma_add_entry_bus(new) < 0) ||
+               (rc = xen_dma_add_entry_phys(new) < 0))
+               return rc;
+       return 0;
+}
+
 static struct xen_dma_info *xen_get_dma_info_from_dma(dma_addr_t dma_addr)
 {
        struct rb_node *n = bus_to_phys.rb_node;
        struct xen_dma_info *entry;
 
        while (n) {
-               entry = rb_entry(n, struct xen_dma_info, rbnode);
+               entry = rb_entry(n, struct xen_dma_info, rbnode_dma);
                if (entry->dma_addr <= dma_addr &&
                                entry->dma_addr + entry->size > dma_addr) {
                        return entry;
@@ -150,11 +198,30 @@ static struct xen_dma_info 
*xen_get_dma_info_from_dma(dma_addr_t dma_addr)
        return NULL;
 }
 
-static dma_addr_t xen_phys_to_bus(phys_addr_t paddr)
+static struct xen_dma_info *xen_get_dma_info_from_phys(phys_addr_t phys)
 {
-       int nr_seg;
-       unsigned long offset;
-       char *vaddr;
+       struct rb_node *n = phys_to_bus.rb_node;
+       struct xen_dma_info *entry;
+
+       while (n) {
+               entry = rb_entry(n, struct xen_dma_info, rbnode_phys);
+               if (entry->phys_addr <= phys &&
+                               entry->phys_addr + entry->size > phys) {
+                       return entry;
+               }
+               if (phys < entry->phys_addr)
+                       n = n->rb_left;
+               else
+                       n = n->rb_right;
+       }
+
+       return NULL;
+}
+
+/* Only looks into the initial buffer allocation in case of
+ * XENFEAT_auto_translated_physmap guests. */
+static dma_addr_t xen_phys_to_bus_quick(phys_addr_t paddr) { int nr_seg;
+       unsigned long offset; char *vaddr;
 
        if (!xen_feature(XENFEAT_auto_translated_physmap))
                return phys_to_machine(XPADDR(paddr)).maddr;
@@ -184,7 +251,7 @@ static phys_addr_t xen_bus_to_phys(dma_addr_t baddr)
 
 static dma_addr_t xen_virt_to_bus(void *address)
 {
-       return xen_phys_to_bus(virt_to_phys(address));
+       return xen_phys_to_bus_quick(virt_to_phys(address));
 }
 
 static int check_pages_physically_contiguous(unsigned long pfn,
@@ -424,7 +491,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t 
size,
         * Do not use virt_to_phys(ret) because on ARM it doesn't correspond
         * to *dma_handle. */
        phys = *dma_handle;
-       dev_addr = xen_phys_to_bus(phys);
+       dev_addr = xen_phys_to_bus_quick(phys);
        if (!xen_feature(XENFEAT_auto_translated_physmap) &&
            ((dev_addr + size - 1 <= dma_mask)) &&
            !range_straddles_page_boundary(phys, size))
@@ -503,7 +570,7 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct 
page *page,
                                struct dma_attrs *attrs)
 {
        phys_addr_t map, phys = page_to_phys(page) + offset;
-       dma_addr_t dev_addr = xen_phys_to_bus(phys);
+       dma_addr_t dev_addr = xen_phys_to_bus_quick(phys);
 
        BUG_ON(dir == DMA_NONE);
        /*
@@ -527,7 +594,7 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct 
page *page,
        if (map == SWIOTLB_MAP_ERROR)
                return DMA_ERROR_CODE;
 
-       dev_addr = xen_phys_to_bus(map);
+       dev_addr = xen_phys_to_bus_quick(map);
 
        /*
         * Ensure that the address returned is DMA'ble
@@ -656,7 +723,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct 
scatterlist *sgl,
 
        for_each_sg(sgl, sg, nelems, i) {
                phys_addr_t paddr = sg_phys(sg);
-               dma_addr_t dev_addr = xen_phys_to_bus(paddr);
+               dma_addr_t dev_addr = xen_phys_to_bus_quick(paddr);
 
                if (swiotlb_force ||
                    xen_feature(XENFEAT_auto_translated_physmap) ||
@@ -682,7 +749,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct 
scatterlist *sgl,
                                sg_dma_len(sgl) = 0;
                                return DMA_ERROR_CODE;
                        }
-                       sg->dma_address = xen_phys_to_bus(map);
+                       sg->dma_address = xen_phys_to_bus_quick(map);
                } else
                        sg->dma_address = dev_addr;
                sg_dma_len(sg) = sg->length;
-- 
1.7.2.5


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