diff mbox series

[28/46] cxl/port: Move dport tracking to an xarray

Message ID 20220624041950.559155-3-dan.j.williams@intel.com
State New
Headers show
Series CXL PMEM Region Provisioning | expand

Commit Message

Dan Williams June 24, 2022, 4:19 a.m. UTC
Reduce the complexity and the overhead of walking the topology to
determine endpoint connectivity to root decoder interleave
configurations.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/acpi.c      |  2 +-
 drivers/cxl/core/hdm.c  |  6 ++-
 drivers/cxl/core/port.c | 88 ++++++++++++++++++-----------------------
 drivers/cxl/cxl.h       | 12 +++---
 4 files changed, 51 insertions(+), 57 deletions(-)

Comments

Jonathan Cameron June 30, 2022, 9:18 a.m. UTC | #1
On Thu, 23 Jun 2022 21:19:32 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> Reduce the complexity and the overhead of walking the topology to
> determine endpoint connectivity to root decoder interleave
> configurations.
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Hi Dan,

A few minor comments inline around naming and also one query on why
the refactor or reap_ports is connected to the xarray change.

Thanks,

Jonathan

> ---
>  drivers/cxl/acpi.c      |  2 +-
>  drivers/cxl/core/hdm.c  |  6 ++-
>  drivers/cxl/core/port.c | 88 ++++++++++++++++++-----------------------
>  drivers/cxl/cxl.h       | 12 +++---
>  4 files changed, 51 insertions(+), 57 deletions(-)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 09fe92177d03..92ad1f359faf 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -197,7 +197,7 @@ static int add_host_bridge_uport(struct device *match, void *arg)
>  	if (!bridge)
>  		return 0;
>  
> -	dport = cxl_find_dport_by_dev(root_port, match);
> +	dport = cxl_dport_load(root_port, match);

Load is kind of specific to the xarray.  I'd be tempted to keep it to
original find naming.


>  	if (!dport) {
>  		dev_dbg(host, "host bridge expected and not found\n");
>  		return 0;
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index c0164f9b2195..672bf3e97811 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -50,8 +50,9 @@ static int add_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
>  int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
>  {
>  	struct cxl_switch_decoder *cxlsd;
> -	struct cxl_dport *dport;
> +	struct cxl_dport *dport = NULL;
>  	int single_port_map[1];
> +	unsigned long index;
>  
>  	cxlsd = cxl_switch_decoder_alloc(port, 1);
>  	if (IS_ERR(cxlsd))
> @@ -59,7 +60,8 @@ int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
>  
>  	device_lock_assert(&port->dev);
>  
> -	dport = list_first_entry(&port->dports, typeof(*dport), list);
> +	xa_for_each(&port->dports, index, dport)
> +		break;
>  	single_port_map[0] = dport->port_id;
>  
>  	return add_hdm_decoder(port, &cxlsd->cxld, single_port_map);
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index ea3ab9baf232..d2f6898940fa 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -452,6 +452,7 @@ static void cxl_port_release(struct device *dev)
>  	xa_for_each(&port->endpoints, index, ep)
>  		cxl_ep_remove(port, ep);
>  	xa_destroy(&port->endpoints);
> +	xa_destroy(&port->dports);
>  	ida_free(&cxl_port_ida, port->id);
>  	kfree(port);
>  }
> @@ -566,7 +567,7 @@ static struct cxl_port *cxl_port_alloc(struct device *uport,
>  	port->component_reg_phys = component_reg_phys;
>  	ida_init(&port->decoder_ida);
>  	port->dpa_end = -1;
> -	INIT_LIST_HEAD(&port->dports);
> +	xa_init(&port->dports);
>  	xa_init(&port->endpoints);
>  
>  	device_initialize(dev);
> @@ -696,17 +697,13 @@ static int match_root_child(struct device *dev, const void *match)
>  		return 0;
>  
>  	port = to_cxl_port(dev);
> -	device_lock(dev);
> -	list_for_each_entry(dport, &port->dports, list) {
> -		iter = match;
> -		while (iter) {
> -			if (iter == dport->dport)
> -				goto out;
> -			iter = iter->parent;
> -		}
> +	iter = match;
> +	while (iter) {
> +		dport = cxl_dport_load(port, iter);
> +		if (dport)
> +			break;
> +		iter = iter->parent;
>  	}
> -out:
> -	device_unlock(dev);
>  
>  	return !!iter;
>  }
> @@ -730,9 +727,10 @@ EXPORT_SYMBOL_NS_GPL(find_cxl_root, CXL);
>  static struct cxl_dport *find_dport(struct cxl_port *port, int id)
>  {
>  	struct cxl_dport *dport;
> +	unsigned long index;
>  
>  	device_lock_assert(&port->dev);
> -	list_for_each_entry (dport, &port->dports, list)
> +	xa_for_each(&port->dports, index, dport)
>  		if (dport->port_id == id)
>  			return dport;
>  	return NULL;
> @@ -741,18 +739,21 @@ static struct cxl_dport *find_dport(struct cxl_port *port, int id)
>  static int add_dport(struct cxl_port *port, struct cxl_dport *new)
>  {
>  	struct cxl_dport *dup;
> +	int rc;
>  
>  	device_lock_assert(&port->dev);
>  	dup = find_dport(port, new->port_id);
> -	if (dup)
> +	if (dup) {
>  		dev_err(&port->dev,
>  			"unable to add dport%d-%s non-unique port id (%s)\n",
>  			new->port_id, dev_name(new->dport),
>  			dev_name(dup->dport));
> -	else
> -		list_add_tail(&new->list, &port->dports);
> +		rc = -EBUSY;

Direct return slightly simpler and reduce indent on next bit plus makes
this more obviously an 'error condition' by indenting it.

> +	} else
> +		rc = xa_insert(&port->dports, (unsigned long)new->dport, new,
> +			       GFP_KERNEL);
>  
> -	return dup ? -EEXIST : 0;
> +	return rc;
>  }
>  
>  /*
> @@ -779,10 +780,8 @@ static void cxl_dport_remove(void *data)
>  	struct cxl_dport *dport = data;
>  	struct cxl_port *port = dport->port;
>  
> +	xa_erase(&port->dports, (unsigned long) dport->dport);
>  	put_device(dport->dport);
> -	cond_cxl_root_lock(port);
> -	list_del(&dport->list);
> -	cond_cxl_root_unlock(port);
>  }
>  
>  static void cxl_dport_unlink(void *data)
> @@ -834,7 +833,6 @@ struct cxl_dport *devm_cxl_add_dport(struct cxl_port *port,
>  	if (!dport)
>  		return ERR_PTR(-ENOMEM);
>  
> -	INIT_LIST_HEAD(&dport->list);
>  	dport->dport = dport_dev;
>  	dport->port_id = port_id;
>  	dport->component_reg_phys = component_reg_phys;
> @@ -925,7 +923,7 @@ static int match_port_by_dport(struct device *dev, const void *data)
>  		return 0;
>  
>  	port = to_cxl_port(dev);
> -	dport = cxl_find_dport_by_dev(port, ctx->dport_dev);
> +	dport = cxl_dport_load(port, ctx->dport_dev);
>  	if (ctx->dport)
>  		*ctx->dport = dport;
>  	return dport != NULL;
> @@ -1025,19 +1023,27 @@ EXPORT_SYMBOL_NS_GPL(cxl_endpoint_autoremove, CXL);
>   * for a port to be unregistered is when all memdevs beneath that port have gone
>   * through ->remove(). This "bottom-up" removal selectively removes individual
>   * child ports manually. This depends on devm_cxl_add_port() to not change is
> - * devm action registration order.
> + * devm action registration order, and for dports to have already been
> + * destroyed by reap_dports().
>   */
> -static void delete_switch_port(struct cxl_port *port, struct list_head *dports)
> +static void delete_switch_port(struct cxl_port *port)
> +{
> +	devm_release_action(port->dev.parent, cxl_unlink_uport, port);
> +	devm_release_action(port->dev.parent, unregister_port, port);
> +}
> +
> +static void reap_dports(struct cxl_port *port)
>  {
> -	struct cxl_dport *dport, *_d;
> +	struct cxl_dport *dport;
> +	unsigned long index;
> +
> +	device_lock_assert(&port->dev);
>  
> -	list_for_each_entry_safe(dport, _d, dports, list) {
> +	xa_for_each(&port->dports, index, dport) {
>  		devm_release_action(&port->dev, cxl_dport_unlink, dport);
>  		devm_release_action(&port->dev, cxl_dport_remove, dport);
>  		devm_kfree(&port->dev, dport);
>  	}
> -	devm_release_action(port->dev.parent, cxl_unlink_uport, port);
> -	devm_release_action(port->dev.parent, unregister_port, port);
>  }
>  
>  static struct cxl_ep *cxl_ep_load(struct cxl_port *port,
> @@ -1054,8 +1060,8 @@ static void cxl_detach_ep(void *data)
>  	for (iter = &cxlmd->dev; iter; iter = grandparent(iter)) {
>  		struct device *dport_dev = grandparent(iter);
>  		struct cxl_port *port, *parent_port;
> -		LIST_HEAD(reap_dports);
>  		struct cxl_ep *ep;
> +		bool died = false;
>  
>  		if (!dport_dev)
>  			break;
> @@ -1095,15 +1101,16 @@ static void cxl_detach_ep(void *data)
>  			 * enumerated port. Block new cxl_add_ep() and garbage
>  			 * collect the port.
>  			 */
> +			died = true;
>  			port->dead = true;
> -			list_splice_init(&port->dports, &reap_dports);
> +			reap_dports(port);

I'm not immediately clear on why this refactor is tied up with moving
to the xarray.  Perhaps a comment in the commit message to add
more detail around this?

>  		}
>  		device_unlock(&port->dev);
>  
> -		if (!list_empty(&reap_dports)) {
> +		if (died) {
>  			dev_dbg(&cxlmd->dev, "delete %s\n",
>  				dev_name(&port->dev));
> -			delete_switch_port(port, &reap_dports);
> +			delete_switch_port(port);
>  		}
>  		put_device(&port->dev);
>  		device_unlock(&parent_port->dev);
> @@ -1282,23 +1289,6 @@ struct cxl_port *cxl_mem_find_port(struct cxl_memdev *cxlmd,
>  }
>  EXPORT_SYMBOL_NS_GPL(cxl_mem_find_port, CXL);
>  
> -struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
> -					const struct device *dev)
> -{
> -	struct cxl_dport *dport;
> -
> -	device_lock(&port->dev);
> -	list_for_each_entry(dport, &port->dports, list)
> -		if (dport->dport == dev) {
> -			device_unlock(&port->dev);
> -			return dport;
> -		}
> -
> -	device_unlock(&port->dev);
> -	return NULL;
> -}
> -EXPORT_SYMBOL_NS_GPL(cxl_find_dport_by_dev, CXL);
> -
>  static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
>  				    struct cxl_port *port, int *target_map)
>  {
> @@ -1309,7 +1299,7 @@ static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
>  
>  	device_lock_assert(&port->dev);
>  
> -	if (list_empty(&port->dports))
> +	if (xa_empty(&port->dports))
>  		return -EINVAL;
>  
>  	write_seqlock(&cxlsd->target_lock);
Dan Williams July 10, 2022, 7:06 p.m. UTC | #2
Jonathan Cameron wrote:
> On Thu, 23 Jun 2022 21:19:32 -0700
> Dan Williams <dan.j.williams@intel.com> wrote:
> 
> > Reduce the complexity and the overhead of walking the topology to
> > determine endpoint connectivity to root decoder interleave
> > configurations.
> > 
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> Hi Dan,
> 
> A few minor comments inline around naming and also one query on why
> the refactor or reap_ports is connected to the xarray change.
> 
> Thanks,
> 
> Jonathan
> 
> > ---
> >  drivers/cxl/acpi.c      |  2 +-
> >  drivers/cxl/core/hdm.c  |  6 ++-
> >  drivers/cxl/core/port.c | 88 ++++++++++++++++++-----------------------
> >  drivers/cxl/cxl.h       | 12 +++---
> >  4 files changed, 51 insertions(+), 57 deletions(-)
> > 
> > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> > index 09fe92177d03..92ad1f359faf 100644
> > --- a/drivers/cxl/acpi.c
> > +++ b/drivers/cxl/acpi.c
> > @@ -197,7 +197,7 @@ static int add_host_bridge_uport(struct device *match, void *arg)
> >  	if (!bridge)
> >  		return 0;
> >  
> > -	dport = cxl_find_dport_by_dev(root_port, match);
> > +	dport = cxl_dport_load(root_port, match);
> 
> Load is kind of specific to the xarray.  I'd be tempted to keep it to
> original find naming.

ok.

> 
> 
> >  	if (!dport) {
> >  		dev_dbg(host, "host bridge expected and not found\n");
> >  		return 0;
> > diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> > index c0164f9b2195..672bf3e97811 100644
> > --- a/drivers/cxl/core/hdm.c
> > +++ b/drivers/cxl/core/hdm.c
> > @@ -50,8 +50,9 @@ static int add_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
> >  int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
> >  {
> >  	struct cxl_switch_decoder *cxlsd;
> > -	struct cxl_dport *dport;
> > +	struct cxl_dport *dport = NULL;
> >  	int single_port_map[1];
> > +	unsigned long index;
> >  
> >  	cxlsd = cxl_switch_decoder_alloc(port, 1);
> >  	if (IS_ERR(cxlsd))
> > @@ -59,7 +60,8 @@ int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
> >  
> >  	device_lock_assert(&port->dev);
> >  
> > -	dport = list_first_entry(&port->dports, typeof(*dport), list);
> > +	xa_for_each(&port->dports, index, dport)
> > +		break;
> >  	single_port_map[0] = dport->port_id;
> >  
> >  	return add_hdm_decoder(port, &cxlsd->cxld, single_port_map);
> > diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> > index ea3ab9baf232..d2f6898940fa 100644
> > --- a/drivers/cxl/core/port.c
> > +++ b/drivers/cxl/core/port.c
> > @@ -452,6 +452,7 @@ static void cxl_port_release(struct device *dev)
> >  	xa_for_each(&port->endpoints, index, ep)
> >  		cxl_ep_remove(port, ep);
> >  	xa_destroy(&port->endpoints);
> > +	xa_destroy(&port->dports);
> >  	ida_free(&cxl_port_ida, port->id);
> >  	kfree(port);
> >  }
> > @@ -566,7 +567,7 @@ static struct cxl_port *cxl_port_alloc(struct device *uport,
> >  	port->component_reg_phys = component_reg_phys;
> >  	ida_init(&port->decoder_ida);
> >  	port->dpa_end = -1;
> > -	INIT_LIST_HEAD(&port->dports);
> > +	xa_init(&port->dports);
> >  	xa_init(&port->endpoints);
> >  
> >  	device_initialize(dev);
> > @@ -696,17 +697,13 @@ static int match_root_child(struct device *dev, const void *match)
> >  		return 0;
> >  
> >  	port = to_cxl_port(dev);
> > -	device_lock(dev);
> > -	list_for_each_entry(dport, &port->dports, list) {
> > -		iter = match;
> > -		while (iter) {
> > -			if (iter == dport->dport)
> > -				goto out;
> > -			iter = iter->parent;
> > -		}
> > +	iter = match;
> > +	while (iter) {
> > +		dport = cxl_dport_load(port, iter);
> > +		if (dport)
> > +			break;
> > +		iter = iter->parent;
> >  	}
> > -out:
> > -	device_unlock(dev);
> >  
> >  	return !!iter;
> >  }
> > @@ -730,9 +727,10 @@ EXPORT_SYMBOL_NS_GPL(find_cxl_root, CXL);
> >  static struct cxl_dport *find_dport(struct cxl_port *port, int id)
> >  {
> >  	struct cxl_dport *dport;
> > +	unsigned long index;
> >  
> >  	device_lock_assert(&port->dev);
> > -	list_for_each_entry (dport, &port->dports, list)
> > +	xa_for_each(&port->dports, index, dport)
> >  		if (dport->port_id == id)
> >  			return dport;
> >  	return NULL;
> > @@ -741,18 +739,21 @@ static struct cxl_dport *find_dport(struct cxl_port *port, int id)
> >  static int add_dport(struct cxl_port *port, struct cxl_dport *new)
> >  {
> >  	struct cxl_dport *dup;
> > +	int rc;
> >  
> >  	device_lock_assert(&port->dev);
> >  	dup = find_dport(port, new->port_id);
> > -	if (dup)
> > +	if (dup) {
> >  		dev_err(&port->dev,
> >  			"unable to add dport%d-%s non-unique port id (%s)\n",
> >  			new->port_id, dev_name(new->dport),
> >  			dev_name(dup->dport));
> > -	else
> > -		list_add_tail(&new->list, &port->dports);
> > +		rc = -EBUSY;
> 
> Direct return slightly simpler and reduce indent on next bit plus makes
> this more obviously an 'error condition' by indenting it.

Looks good, yes.

> 
> > +	} else
> > +		rc = xa_insert(&port->dports, (unsigned long)new->dport, new,
> > +			       GFP_KERNEL);
> >  
> > -	return dup ? -EEXIST : 0;
> > +	return rc;
> >  }
> >  
> >  /*
> > @@ -779,10 +780,8 @@ static void cxl_dport_remove(void *data)
> >  	struct cxl_dport *dport = data;
> >  	struct cxl_port *port = dport->port;
> >  
> > +	xa_erase(&port->dports, (unsigned long) dport->dport);
> >  	put_device(dport->dport);
> > -	cond_cxl_root_lock(port);
> > -	list_del(&dport->list);
> > -	cond_cxl_root_unlock(port);
> >  }
> >  
> >  static void cxl_dport_unlink(void *data)
> > @@ -834,7 +833,6 @@ struct cxl_dport *devm_cxl_add_dport(struct cxl_port *port,
> >  	if (!dport)
> >  		return ERR_PTR(-ENOMEM);
> >  
> > -	INIT_LIST_HEAD(&dport->list);
> >  	dport->dport = dport_dev;
> >  	dport->port_id = port_id;
> >  	dport->component_reg_phys = component_reg_phys;
> > @@ -925,7 +923,7 @@ static int match_port_by_dport(struct device *dev, const void *data)
> >  		return 0;
> >  
> >  	port = to_cxl_port(dev);
> > -	dport = cxl_find_dport_by_dev(port, ctx->dport_dev);
> > +	dport = cxl_dport_load(port, ctx->dport_dev);
> >  	if (ctx->dport)
> >  		*ctx->dport = dport;
> >  	return dport != NULL;
> > @@ -1025,19 +1023,27 @@ EXPORT_SYMBOL_NS_GPL(cxl_endpoint_autoremove, CXL);
> >   * for a port to be unregistered is when all memdevs beneath that port have gone
> >   * through ->remove(). This "bottom-up" removal selectively removes individual
> >   * child ports manually. This depends on devm_cxl_add_port() to not change is
> > - * devm action registration order.
> > + * devm action registration order, and for dports to have already been
> > + * destroyed by reap_dports().
> >   */
> > -static void delete_switch_port(struct cxl_port *port, struct list_head *dports)
> > +static void delete_switch_port(struct cxl_port *port)
> > +{
> > +	devm_release_action(port->dev.parent, cxl_unlink_uport, port);
> > +	devm_release_action(port->dev.parent, unregister_port, port);
> > +}
> > +
> > +static void reap_dports(struct cxl_port *port)
> >  {
> > -	struct cxl_dport *dport, *_d;
> > +	struct cxl_dport *dport;
> > +	unsigned long index;
> > +
> > +	device_lock_assert(&port->dev);
> >  
> > -	list_for_each_entry_safe(dport, _d, dports, list) {
> > +	xa_for_each(&port->dports, index, dport) {
> >  		devm_release_action(&port->dev, cxl_dport_unlink, dport);
> >  		devm_release_action(&port->dev, cxl_dport_remove, dport);
> >  		devm_kfree(&port->dev, dport);
> >  	}
> > -	devm_release_action(port->dev.parent, cxl_unlink_uport, port);
> > -	devm_release_action(port->dev.parent, unregister_port, port);
> >  }
> >  
> >  static struct cxl_ep *cxl_ep_load(struct cxl_port *port,
> > @@ -1054,8 +1060,8 @@ static void cxl_detach_ep(void *data)
> >  	for (iter = &cxlmd->dev; iter; iter = grandparent(iter)) {
> >  		struct device *dport_dev = grandparent(iter);
> >  		struct cxl_port *port, *parent_port;
> > -		LIST_HEAD(reap_dports);
> >  		struct cxl_ep *ep;
> > +		bool died = false;
> >  
> >  		if (!dport_dev)
> >  			break;
> > @@ -1095,15 +1101,16 @@ static void cxl_detach_ep(void *data)
> >  			 * enumerated port. Block new cxl_add_ep() and garbage
> >  			 * collect the port.
> >  			 */
> > +			died = true;
> >  			port->dead = true;
> > -			list_splice_init(&port->dports, &reap_dports);
> > +			reap_dports(port);
> 
> I'm not immediately clear on why this refactor is tied up with moving
> to the xarray.  Perhaps a comment in the commit message to add
> more detail around this?

Sure, added the following:

   Note that cxl_detach_ep(), after it determines that the last @ep has
   departed and decides to delete the port, now needs to walk the dport
   array with the device_lock() held to remove entries. Previously
   list_splice_init() could be used atomically delete all dport entries at
   once and then perform entry tear down outside the lock. There is no
   list_splice_init() equivalent for the xarray.
diff mbox series

Patch

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index 09fe92177d03..92ad1f359faf 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -197,7 +197,7 @@  static int add_host_bridge_uport(struct device *match, void *arg)
 	if (!bridge)
 		return 0;
 
-	dport = cxl_find_dport_by_dev(root_port, match);
+	dport = cxl_dport_load(root_port, match);
 	if (!dport) {
 		dev_dbg(host, "host bridge expected and not found\n");
 		return 0;
diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index c0164f9b2195..672bf3e97811 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -50,8 +50,9 @@  static int add_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
 int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
 {
 	struct cxl_switch_decoder *cxlsd;
-	struct cxl_dport *dport;
+	struct cxl_dport *dport = NULL;
 	int single_port_map[1];
+	unsigned long index;
 
 	cxlsd = cxl_switch_decoder_alloc(port, 1);
 	if (IS_ERR(cxlsd))
@@ -59,7 +60,8 @@  int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
 
 	device_lock_assert(&port->dev);
 
-	dport = list_first_entry(&port->dports, typeof(*dport), list);
+	xa_for_each(&port->dports, index, dport)
+		break;
 	single_port_map[0] = dport->port_id;
 
 	return add_hdm_decoder(port, &cxlsd->cxld, single_port_map);
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index ea3ab9baf232..d2f6898940fa 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -452,6 +452,7 @@  static void cxl_port_release(struct device *dev)
 	xa_for_each(&port->endpoints, index, ep)
 		cxl_ep_remove(port, ep);
 	xa_destroy(&port->endpoints);
+	xa_destroy(&port->dports);
 	ida_free(&cxl_port_ida, port->id);
 	kfree(port);
 }
@@ -566,7 +567,7 @@  static struct cxl_port *cxl_port_alloc(struct device *uport,
 	port->component_reg_phys = component_reg_phys;
 	ida_init(&port->decoder_ida);
 	port->dpa_end = -1;
-	INIT_LIST_HEAD(&port->dports);
+	xa_init(&port->dports);
 	xa_init(&port->endpoints);
 
 	device_initialize(dev);
@@ -696,17 +697,13 @@  static int match_root_child(struct device *dev, const void *match)
 		return 0;
 
 	port = to_cxl_port(dev);
-	device_lock(dev);
-	list_for_each_entry(dport, &port->dports, list) {
-		iter = match;
-		while (iter) {
-			if (iter == dport->dport)
-				goto out;
-			iter = iter->parent;
-		}
+	iter = match;
+	while (iter) {
+		dport = cxl_dport_load(port, iter);
+		if (dport)
+			break;
+		iter = iter->parent;
 	}
-out:
-	device_unlock(dev);
 
 	return !!iter;
 }
@@ -730,9 +727,10 @@  EXPORT_SYMBOL_NS_GPL(find_cxl_root, CXL);
 static struct cxl_dport *find_dport(struct cxl_port *port, int id)
 {
 	struct cxl_dport *dport;
+	unsigned long index;
 
 	device_lock_assert(&port->dev);
-	list_for_each_entry (dport, &port->dports, list)
+	xa_for_each(&port->dports, index, dport)
 		if (dport->port_id == id)
 			return dport;
 	return NULL;
@@ -741,18 +739,21 @@  static struct cxl_dport *find_dport(struct cxl_port *port, int id)
 static int add_dport(struct cxl_port *port, struct cxl_dport *new)
 {
 	struct cxl_dport *dup;
+	int rc;
 
 	device_lock_assert(&port->dev);
 	dup = find_dport(port, new->port_id);
-	if (dup)
+	if (dup) {
 		dev_err(&port->dev,
 			"unable to add dport%d-%s non-unique port id (%s)\n",
 			new->port_id, dev_name(new->dport),
 			dev_name(dup->dport));
-	else
-		list_add_tail(&new->list, &port->dports);
+		rc = -EBUSY;
+	} else
+		rc = xa_insert(&port->dports, (unsigned long)new->dport, new,
+			       GFP_KERNEL);
 
-	return dup ? -EEXIST : 0;
+	return rc;
 }
 
 /*
@@ -779,10 +780,8 @@  static void cxl_dport_remove(void *data)
 	struct cxl_dport *dport = data;
 	struct cxl_port *port = dport->port;
 
+	xa_erase(&port->dports, (unsigned long) dport->dport);
 	put_device(dport->dport);
-	cond_cxl_root_lock(port);
-	list_del(&dport->list);
-	cond_cxl_root_unlock(port);
 }
 
 static void cxl_dport_unlink(void *data)
@@ -834,7 +833,6 @@  struct cxl_dport *devm_cxl_add_dport(struct cxl_port *port,
 	if (!dport)
 		return ERR_PTR(-ENOMEM);
 
-	INIT_LIST_HEAD(&dport->list);
 	dport->dport = dport_dev;
 	dport->port_id = port_id;
 	dport->component_reg_phys = component_reg_phys;
@@ -925,7 +923,7 @@  static int match_port_by_dport(struct device *dev, const void *data)
 		return 0;
 
 	port = to_cxl_port(dev);
-	dport = cxl_find_dport_by_dev(port, ctx->dport_dev);
+	dport = cxl_dport_load(port, ctx->dport_dev);
 	if (ctx->dport)
 		*ctx->dport = dport;
 	return dport != NULL;
@@ -1025,19 +1023,27 @@  EXPORT_SYMBOL_NS_GPL(cxl_endpoint_autoremove, CXL);
  * for a port to be unregistered is when all memdevs beneath that port have gone
  * through ->remove(). This "bottom-up" removal selectively removes individual
  * child ports manually. This depends on devm_cxl_add_port() to not change is
- * devm action registration order.
+ * devm action registration order, and for dports to have already been
+ * destroyed by reap_dports().
  */
-static void delete_switch_port(struct cxl_port *port, struct list_head *dports)
+static void delete_switch_port(struct cxl_port *port)
+{
+	devm_release_action(port->dev.parent, cxl_unlink_uport, port);
+	devm_release_action(port->dev.parent, unregister_port, port);
+}
+
+static void reap_dports(struct cxl_port *port)
 {
-	struct cxl_dport *dport, *_d;
+	struct cxl_dport *dport;
+	unsigned long index;
+
+	device_lock_assert(&port->dev);
 
-	list_for_each_entry_safe(dport, _d, dports, list) {
+	xa_for_each(&port->dports, index, dport) {
 		devm_release_action(&port->dev, cxl_dport_unlink, dport);
 		devm_release_action(&port->dev, cxl_dport_remove, dport);
 		devm_kfree(&port->dev, dport);
 	}
-	devm_release_action(port->dev.parent, cxl_unlink_uport, port);
-	devm_release_action(port->dev.parent, unregister_port, port);
 }
 
 static struct cxl_ep *cxl_ep_load(struct cxl_port *port,
@@ -1054,8 +1060,8 @@  static void cxl_detach_ep(void *data)
 	for (iter = &cxlmd->dev; iter; iter = grandparent(iter)) {
 		struct device *dport_dev = grandparent(iter);
 		struct cxl_port *port, *parent_port;
-		LIST_HEAD(reap_dports);
 		struct cxl_ep *ep;
+		bool died = false;
 
 		if (!dport_dev)
 			break;
@@ -1095,15 +1101,16 @@  static void cxl_detach_ep(void *data)
 			 * enumerated port. Block new cxl_add_ep() and garbage
 			 * collect the port.
 			 */
+			died = true;
 			port->dead = true;
-			list_splice_init(&port->dports, &reap_dports);
+			reap_dports(port);
 		}
 		device_unlock(&port->dev);
 
-		if (!list_empty(&reap_dports)) {
+		if (died) {
 			dev_dbg(&cxlmd->dev, "delete %s\n",
 				dev_name(&port->dev));
-			delete_switch_port(port, &reap_dports);
+			delete_switch_port(port);
 		}
 		put_device(&port->dev);
 		device_unlock(&parent_port->dev);
@@ -1282,23 +1289,6 @@  struct cxl_port *cxl_mem_find_port(struct cxl_memdev *cxlmd,
 }
 EXPORT_SYMBOL_NS_GPL(cxl_mem_find_port, CXL);
 
-struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
-					const struct device *dev)
-{
-	struct cxl_dport *dport;
-
-	device_lock(&port->dev);
-	list_for_each_entry(dport, &port->dports, list)
-		if (dport->dport == dev) {
-			device_unlock(&port->dev);
-			return dport;
-		}
-
-	device_unlock(&port->dev);
-	return NULL;
-}
-EXPORT_SYMBOL_NS_GPL(cxl_find_dport_by_dev, CXL);
-
 static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
 				    struct cxl_port *port, int *target_map)
 {
@@ -1309,7 +1299,7 @@  static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
 
 	device_lock_assert(&port->dev);
 
-	if (list_empty(&port->dports))
+	if (xa_empty(&port->dports))
 		return -EINVAL;
 
 	write_seqlock(&cxlsd->target_lock);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 3d149780d724..8e2c1b393552 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -336,7 +336,7 @@  struct cxl_port {
 	struct device dev;
 	struct device *uport;
 	int id;
-	struct list_head dports;
+	struct xarray dports;
 	struct xarray endpoints;
 	struct cxl_dport *parent_dport;
 	struct ida decoder_ida;
@@ -346,20 +346,24 @@  struct cxl_port {
 	unsigned int depth;
 };
 
+static inline struct cxl_dport *cxl_dport_load(struct cxl_port *port,
+					       const struct device *dport_dev)
+{
+	return xa_load(&port->dports, (unsigned long)dport_dev);
+}
+
 /**
  * struct cxl_dport - CXL downstream port
  * @dport: PCI bridge or firmware device representing the downstream link
  * @port_id: unique hardware identifier for dport in decoder target list
  * @component_reg_phys: downstream port component registers
  * @port: reference to cxl_port that contains this downstream port
- * @list: node for a cxl_port's list of cxl_dport instances
  */
 struct cxl_dport {
 	struct device *dport;
 	int port_id;
 	resource_size_t component_reg_phys;
 	struct cxl_port *port;
-	struct list_head list;
 };
 
 /**
@@ -402,8 +406,6 @@  bool schedule_cxl_memdev_detach(struct cxl_memdev *cxlmd);
 struct cxl_dport *devm_cxl_add_dport(struct cxl_port *port,
 				     struct device *dport, int port_id,
 				     resource_size_t component_reg_phys);
-struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
-					const struct device *dev);
 
 struct cxl_decoder *to_cxl_decoder(struct device *dev);
 struct cxl_root_decoder *to_cxl_root_decoder(struct device *dev);