[PATCH 04/14] PCI/P2PDMA: Cache the result of upstream_bridge_distance()

[Logan Gunthorpe]

The result of upstream_bridge_distance() will be needed every time
we map the dma address so cache it in an xarray stored in the
provider's p2pdma struct.

Signed-off-by: Logan Gunthorpe <log...@deltatee.com>
---
 drivers/pci/p2pdma.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index d5034e28d1e1..25663c1d8bc9 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -19,10 +19,12 @@
 #include <linux/random.h>
 #include <linux/seq_buf.h>
 #include <linux/iommu.h>
+#include <linux/xarray.h>
 
 struct pci_p2pdma {
        struct gen_pool *pool;
        bool p2pmem_published;
+       struct xarray dist_cache;
 };
 
 static ssize_t size_show(struct device *dev, struct device_attribute *attr,
@@ -98,6 +100,8 @@ static int pci_p2pdma_setup(struct pci_dev *pdev)
        if (!p2p)
                return -ENOMEM;
 
+       xa_init(&p2p->dist_cache);
+
        p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));
        if (!p2p->pool)
                goto out;
@@ -390,17 +394,34 @@ static int upstream_bridge_distance(struct pci_dev 
*provider,
                                    struct pci_dev *client,
                                    struct seq_buf *acs_list)
 {
+       void *entry;
        int dist;
+       int idx;
+
+       idx = (pci_domain_nr(client->bus) << 16) |
+               (client->bus->number << 8) | client->devfn;
+
+       if (provider->p2pdma) {
+               entry = xa_load(&provider->p2pdma->dist_cache, idx);
+               if (entry)
+                       return xa_to_value(entry);
+       }
 
        dist = __upstream_bridge_distance(provider, client, acs_list);
 
        if (!(dist & P2PDMA_THRU_HOST_BRIDGE))
-               return dist;
+               goto store_and_return;
+
+       if (!root_complex_whitelist(provider) ||
+           !root_complex_whitelist(client))
+               dist |= P2PDMA_NOT_SUPPORTED;
 
-       if (root_complex_whitelist(provider) && root_complex_whitelist(client))
-               return dist;
+store_and_return:
+       if (provider->p2pdma)
+               xa_store(&provider->p2pdma->dist_cache, idx,
+                        xa_mk_value(dist), GFP_KERNEL);
 
-       return dist | P2PDMA_NOT_SUPPORTED;
+       return dist;
 }
 
 static int upstream_bridge_distance_warn(struct pci_dev *provider,
-- 
2.20.1