Re: [PATCH v19 18/22] cxl: Allow region creation by type2 drivers

Dave Jiang
2025-10-15T21:36:56Z

On 10/6/25 3:01 AM, alejandro.lucero-palau@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
>
> Creating a CXL region requires userspace intervention through the cxl
> sysfs files. Type2 support should allow accelerator drivers to create
> such cxl region from kernel code.
>
> Adding that functionality and integrating it with current support for
> memory expanders.
>
> Support an action by the type2 driver to be linked to the created region
> for unwinding the resources allocated properly.
>
> Based on https://lore.kernel.org/linux-cxl/168592159835.1948938.1647215579839222774.stgit@dwillia2-xfh.jf.intel.com/
>
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
> drivers/cxl/core/core.h | 5 --
> drivers/cxl/core/region.c | 134 +++++++++++++++++++++++++++++++++++---
> drivers/cxl/port.c | 5 +-
> include/cxl/cxl.h | 11 ++++
> 4 files changed, 141 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index c4dddbec5d6e..83abaca9f418 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -14,11 +14,6 @@ extern const struct device_type cxl_pmu_type;
>
> extern struct attribute_group cxl_base_attribute_group;
>
> -enum cxl_detach_mode {
> - DETACH_ONLY,
> - DETACH_INVALIDATE,
> -};
> -
> #ifdef CONFIG_CXL_REGION
> extern struct device_attribute dev_attr_create_pmem_region;
> extern struct device_attribute dev_attr_create_ram_region;
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 26dfc15e57cd..e3b6d85cd43e 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2375,6 +2375,7 @@ int cxl_decoder_detach(struct cxl_region *cxlr,
> }
> return 0;
> }
> +EXPORT_SYMBOL_NS_GPL(cxl_decoder_detach, "CXL");
>
> static int __attach_target(struct cxl_region *cxlr,
> struct cxl_endpoint_decoder *cxled, int pos,
> @@ -2860,6 +2861,14 @@ cxl_find_region_by_name(struct cxl_root_decoder *cxlrd, const char *name)
> return to_cxl_region(region_dev);
> }
>
> +static void drop_region(struct cxl_region *cxlr)
> +{
> + struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
> + struct cxl_port *port = cxlrd_to_port(cxlrd);
> +
> + devm_release_action(port->uport_dev, unregister_region, cxlr);
> +}
> +
> static ssize_t delete_region_store(struct device *dev,
> struct device_attribute *attr,
> const char *buf, size_t len)
> @@ -3588,14 +3597,12 @@ static int __construct_region(struct cxl_region *cxlr,
> return 0;
> }
>
> -/* Establish an empty region covering the given HPA range */
> -static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> - struct cxl_endpoint_decoder *cxled)
> +static struct cxl_region *construct_region_begin(struct cxl_root_decoder *cxlrd,
> + struct cxl_endpoint_decoder *cxled)
> {
> struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> - struct cxl_port *port = cxlrd_to_port(cxlrd);
> struct cxl_dev_state *cxlds = cxlmd->cxlds;
> - int rc, part = READ_ONCE(cxled->part);
> + int part = READ_ONCE(cxled->part);
> struct cxl_region *cxlr;
>
> do {
> @@ -3604,13 +3611,24 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> cxled->cxld.target_type);
> } while (IS_ERR(cxlr) && PTR_ERR(cxlr) == -EBUSY);
>
> - if (IS_ERR(cxlr)) {
> + if (IS_ERR(cxlr))
> dev_err(cxlmd->dev.parent,
> "%s:%s: %s failed assign region: %ld\n",
> dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
> __func__, PTR_ERR(cxlr));
> - return cxlr;
> - }
> +
> + return cxlr;
> +}
> +
> +/* Establish an empty region covering the given HPA range */
> +static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> + struct cxl_endpoint_decoder *cxled)
> +{
> + struct cxl_port *port = cxlrd_to_port(cxlrd);
> + struct cxl_region *cxlr;
> + int rc;
> +
> + cxlr = construct_region_begin(cxlrd, cxled);

Need to check the returned cxlr.

DJ

>
> rc = __construct_region(cxlr, cxlrd, cxled);
> if (rc) {
> @@ -3621,6 +3639,106 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> return cxlr;
> }
>
> +DEFINE_FREE(cxl_region_drop, struct cxl_region *, if (_T) drop_region(_T))
> +
> +static struct cxl_region *
> +__construct_new_region(struct cxl_root_decoder *cxlrd,
> + struct cxl_endpoint_decoder **cxled, int ways)
> +{
> + struct cxl_memdev *cxlmd = cxled_to_memdev(cxled[0]);
> + struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
> + struct cxl_region_params *p;
> + resource_size_t size = 0;
> + int rc, i;
> +
> + struct cxl_region *cxlr __free(cxl_region_drop) =
> + construct_region_begin(cxlrd, cxled[0]);
> + if (IS_ERR(cxlr))
> + return cxlr;
> +
> + guard(rwsem_write)(&cxl_rwsem.region);
> +
> + /*
> + * Sanity check. This should not happen with an accel driver handling
> + * the region creation.
> + */
> + p = &cxlr->params;
> + if (p->state >= CXL_CONFIG_INTERLEAVE_ACTIVE) {
> + dev_err(cxlmd->dev.parent,
> + "%s:%s: %s unexpected region state\n",
> + dev_name(&cxlmd->dev), dev_name(&cxled[0]->cxld.dev),
> + __func__);
> + return ERR_PTR(-EBUSY);
> + }
> +
> + rc = set_interleave_ways(cxlr, ways);
> + if (rc)
> + return ERR_PTR(rc);
> +
> + rc = set_interleave_granularity(cxlr, cxld->interleave_granularity);
> + if (rc)
> + return ERR_PTR(rc);
> +
> + scoped_guard(rwsem_read, &cxl_rwsem.dpa) {
> + for (i = 0; i < ways; i++) {
> + if (!cxled[i]->dpa_res)
> + break;
> + size += resource_size(cxled[i]->dpa_res);
> + }
> + if (i < ways)
> + return ERR_PTR(-EINVAL);
> +
> + rc = alloc_hpa(cxlr, size);
> + if (rc)
> + return ERR_PTR(rc);
> +
> + for (i = 0; i < ways; i++) {
> + rc = cxl_region_attach(cxlr, cxled[i], 0);
> + if (rc)
> + return ERR_PTR(rc);
> + }
> + }
> +
> + rc = cxl_region_decode_commit(cxlr);
> + if (rc)
> + return ERR_PTR(rc);
> +
> + p->state = CXL_CONFIG_COMMIT;
> +
> + return no_free_ptr(cxlr);
> +}
> +
> +/**
> + * cxl_create_region - Establish a region given an endpoint decoder
> + * @cxlrd: root decoder to allocate HPA
> + * @cxled: endpoint decoders with reserved DPA capacity
> + * @ways: interleave ways required
> + *
> + * Returns a fully formed region in the commit state and attached to the
> + * cxl_region driver.
> + */
> +struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
> + struct cxl_endpoint_decoder **cxled,
> + int ways)
> +{
> + struct cxl_region *cxlr;
> +
> + mutex_lock(&cxlrd->range_lock);
> + cxlr = __construct_new_region(cxlrd, cxled, ways);
> + mutex_unlock(&cxlrd->range_lock);
> + if (IS_ERR(cxlr))
> + return cxlr;
> +
> + if (device_attach(&cxlr->dev) <= 0) {
> + dev_err(&cxlr->dev, "failed to create region\n");
> + drop_region(cxlr);
> + return ERR_PTR(-ENODEV);
> + }
> +
> + return cxlr;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_create_region, "CXL");
> +
> static struct cxl_region *
> cxl_find_region_by_range(struct cxl_root_decoder *cxlrd, struct range *hpa)
> {
> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> index 83f5a09839ab..e6c0bd0fc9f9 100644
> --- a/drivers/cxl/port.c
> +++ b/drivers/cxl/port.c
> @@ -35,6 +35,7 @@ static void schedule_detach(void *cxlmd)
> static int discover_region(struct device *dev, void *unused)
> {
> struct cxl_endpoint_decoder *cxled;
> + struct cxl_memdev *cxlmd;
> int rc;
>
> if (!is_endpoint_decoder(dev))
> @@ -44,7 +45,9 @@ static int discover_region(struct device *dev, void *unused)
> if ((cxled->cxld.flags & CXL_DECODER_F_ENABLE) == 0)
> return 0;
>
> - if (cxled->state != CXL_DECODER_STATE_AUTO)
> + cxlmd = cxled_to_memdev(cxled);
> + if (cxled->state != CXL_DECODER_STATE_AUTO ||
> + cxlmd->cxlds->type == CXL_DEVTYPE_DEVMEM)
> return 0;
>
> /*
> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> index 1cbe53ad0416..c6fd8fbd36c4 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h
> @@ -275,4 +275,15 @@ struct cxl_endpoint_decoder *cxl_request_dpa(struct cxl_memdev *cxlmd,
> enum cxl_partition_mode mode,
> resource_size_t alloc);
> int cxl_dpa_free(struct cxl_endpoint_decoder *cxled);
> +struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
> + struct cxl_endpoint_decoder **cxled,
> + int ways);
> +enum cxl_detach_mode {
> + DETACH_ONLY,
> + DETACH_INVALIDATE,
> +};
> +
> +int cxl_decoder_detach(struct cxl_region *cxlr,
> + struct cxl_endpoint_decoder *cxled, int pos,
> + enum cxl_detach_mode mode);
> #endif /* __CXL_CXL_H__ */