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