cxl/memdev: Fix endpoint port removal

Testing of ram region support [1], stimulates a long standing bug in
cxl_detach_ep() where some cxl_ep_remove() cleanup is skipped due to
inability to walk ports after dports have been unregistered. That
results in a failure to re-register a memdev after the port is
re-enabled leading to a crash like the following:

    cxl_port_setup_targets: cxl region4: cxl_host_bridge.0:port4 iw: 1 ig: 256
    general protection fault, ...
    [..]
    RIP: 0010:cxl_region_setup_targets+0x897/0x9e0 [cxl_core]
    dev_name at include/linux/device.h:700
    (inlined by) cxl_port_setup_targets at drivers/cxl/core/region.c:1155
    (inlined by) cxl_region_setup_targets at drivers/cxl/core/region.c:1249
    [..]
    Call Trace:
     <TASK>
     attach_target+0x39a/0x760 [cxl_core]
     ? __mutex_unlock_slowpath+0x3a/0x290
     cxl_add_to_region+0xb8/0x340 [cxl_core]
     ? lockdep_hardirqs_on+0x7d/0x100
     discover_region+0x4b/0x80 [cxl_port]
     ? __pfx_discover_region+0x10/0x10 [cxl_port]
     device_for_each_child+0x58/0x90
     cxl_port_probe+0x10e/0x130 [cxl_port]
     cxl_bus_probe+0x17/0x50 [cxl_core]

Change the port ancestry walk to be by depth rather than by dport. This
ensures that even if a port has unregistered its dports a deferred
memdev cleanup will still be able to cleanup the memdev's interest in
that port.

The parent_port->dev.driver check is only needed for determining if the
bottom up removal beat the top-down removal, but cxl_ep_remove() can
always proceed given the port is pinned. That is, the two sources of
cxl_ep_remove() are in cxl_detach_ep() and cxl_port_release(), and
cxl_port_release() can not run if cxl_detach_ep() holds a reference.

Fixes: 2703c16c75ae ("cxl/core/port: Add switch port enumeration")
Link: http://lore.kernel.org/r/167564534874.847146.5222419648551436750.stgit@dwillia2-xfh.jf.intel.com
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/167601992789.1924368.8083994227892600608.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index a74a93310d26d1fa2cd369248955c50801135531..3a8bc2b060477fd9db772479b8a8f9405052ddb6 100644 (file)
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -246,6 +246,7 @@ static struct cxl_memdev *cxl_memdev_alloc(struct cxl_dev_state *cxlds,
        if (rc < 0)
                goto err;
        cxlmd->id = rc;
+       cxlmd->depth = -1;
 
        dev = &cxlmd->dev;
        device_initialize(dev);

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 410c036c09fa5f4f36820df06ea7d3a9401d1492..317bcf4dbd9d22c3608c57cae419a1736728523d 100644 (file)
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -1207,6 +1207,7 @@ int cxl_endpoint_autoremove(struct cxl_memdev *cxlmd, struct cxl_port *endpoint)
 
        get_device(&endpoint->dev);
        dev_set_drvdata(dev, endpoint);
+       cxlmd->depth = endpoint->depth;
        return devm_add_action_or_reset(dev, delete_endpoint, cxlmd);
 }
 EXPORT_SYMBOL_NS_GPL(cxl_endpoint_autoremove, CXL);
@@ -1241,50 +1242,55 @@ static void reap_dports(struct cxl_port *port)
        }
 }
 
+struct detach_ctx {
+       struct cxl_memdev *cxlmd;
+       int depth;
+};
+
+static int port_has_memdev(struct device *dev, const void *data)
+{
+       const struct detach_ctx *ctx = data;
+       struct cxl_port *port;
+
+       if (!is_cxl_port(dev))
+               return 0;
+
+       port = to_cxl_port(dev);
+       if (port->depth != ctx->depth)
+               return 0;
+
+       return !!cxl_ep_load(port, ctx->cxlmd);
+}
+
 static void cxl_detach_ep(void *data)
 {
        struct cxl_memdev *cxlmd = data;
-       struct device *iter;
 
-       for (iter = &cxlmd->dev; iter; iter = grandparent(iter)) {
-               struct device *dport_dev = grandparent(iter);
+       for (int i = cxlmd->depth - 1; i >= 1; i--) {
                struct cxl_port *port, *parent_port;
+               struct detach_ctx ctx = {
+                       .cxlmd = cxlmd,
+                       .depth = i,
+               };
+               struct device *dev;
                struct cxl_ep *ep;
                bool died = false;
 
-               if (!dport_dev)
-                       break;
-
-               port = find_cxl_port(dport_dev, NULL);
-               if (!port)
-                       continue;
-
-               if (is_cxl_root(port)) {
-                       put_device(&port->dev);
+               dev = bus_find_device(&cxl_bus_type, NULL, &ctx,
+                                     port_has_memdev);
+               if (!dev)
                        continue;
-               }
+               port = to_cxl_port(dev);
 
                parent_port = to_cxl_port(port->dev.parent);
                device_lock(&parent_port->dev);
-               if (!parent_port->dev.driver) {
-                       /*
-                        * The bottom-up race to delete the port lost to a
-                        * top-down port disable, give up here, because the
-                        * parent_port ->remove() will have cleaned up all
-                        * descendants.
-                        */
-                       device_unlock(&parent_port->dev);
-                       put_device(&port->dev);
-                       continue;
-               }
-
                device_lock(&port->dev);
                ep = cxl_ep_load(port, cxlmd);
                dev_dbg(&cxlmd->dev, "disconnect %s from %s\n",
                        ep ? dev_name(ep->ep) : "", dev_name(&port->dev));
                cxl_ep_remove(port, ep);
                if (ep && !port->dead && xa_empty(&port->endpoints) &&
-                   !is_cxl_root(parent_port)) {
+                   !is_cxl_root(parent_port) && parent_port->dev.driver) {
                        /*
                         * This was the last ep attached to a dynamically
                         * enumerated port. Block new cxl_add_ep() and garbage

diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index ab138004f644820e94c0b7d950e8c9d004288ddc..c9da3c699a212f03d090c1338f82cbc1588ca560 100644 (file)
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -38,6 +38,7 @@
  * @cxl_nvb: coordinate removal of @cxl_nvd if present
  * @cxl_nvd: optional bridge to an nvdimm if the device supports pmem
  * @id: id number of this memdev instance.
+ * @depth: endpoint port depth
  */
 struct cxl_memdev {
        struct device dev;
@@ -47,6 +48,7 @@ struct cxl_memdev {
        struct cxl_nvdimm_bridge *cxl_nvb;
        struct cxl_nvdimm *cxl_nvd;
        int id;
+       int depth;
 };
 
 static inline struct cxl_memdev *to_cxl_memdev(struct device *dev)