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Message-ID: <9913bfa1-c612-4b51-8b53-4b5449c8dd30@intel.com>
Date: Fri, 11 Apr 2025 16:18:52 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: alejandro.lucero-palau@....com, linux-cxl@...r.kernel.org,
netdev@...r.kernel.org, dan.j.williams@...el.com, edward.cree@....com,
davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com
Cc: Alejandro Lucero <alucerop@....com>
Subject: Re: [PATCH v12 18/23] cxl: allow region creation by type2 drivers
On 3/31/25 7:45 AM, alejandro.lucero-palau@....com wrote:
> From: Alejandro Lucero <alucerop@....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.
>
> Based on https://lore.kernel.org/linux-cxl/168592159835.1948938.1647215579839222774.stgit@dwillia2-xfh.jf.intel.com/
>
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> ---
> drivers/cxl/core/region.c | 135 +++++++++++++++++++++++++++++++++++---
> drivers/cxl/port.c | 5 +-
> include/cxl/cxl.h | 4 ++
> 3 files changed, 135 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 892fb799bf46..f2e1d5719a70 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2310,6 +2310,17 @@ static int cxl_region_detach(struct cxl_endpoint_decoder *cxled)
> return rc;
> }
>
> +int cxl_accel_region_detach(struct cxl_endpoint_decoder *cxled)
> +{
> + int rc;
> +
> + guard(rwsem_write)(&cxl_region_rwsem);
> + cxled->part = -1;
> + rc = cxl_region_detach(cxled);
> + return rc;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_accel_region_detach, "CXL");
> +
> void cxl_decoder_kill_region(struct cxl_endpoint_decoder *cxled)
> {
> down_write(&cxl_region_rwsem);
> @@ -2816,6 +2827,14 @@ 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)
> @@ -3520,14 +3539,12 @@ 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 {
> @@ -3536,13 +3553,23 @@ 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);
>
> rc = __construct_region(cxlr, cxlrd, cxled);
> if (rc) {
> @@ -3553,6 +3580,98 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> return cxlr;
> }
>
> +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);
> + struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
> + struct cxl_region_params *p;
> + struct cxl_region *cxlr;
> + int rc;
> +
> + cxlr = construct_region_begin(cxlrd, cxled);
> + if (IS_ERR(cxlr))
> + return cxlr;
> +
> + guard(rwsem_write)(&cxl_region_rwsem);
> +
> + /*
> + * 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->cxld.dev),
> + __func__);
> + rc = -EBUSY;
> + goto err;
> + }
> +
> + rc = set_interleave_ways(cxlr, ways);
> + if (rc)
> + goto err;
> +
> + rc = set_interleave_granularity(cxlr, cxld->interleave_granularity);
> + if (rc)
> + goto err;
> +
> + rc = alloc_hpa(cxlr, resource_size(cxled->dpa_res));
> + if (rc)
> + goto err;
> +
> + down_read(&cxl_dpa_rwsem);
> + rc = cxl_region_attach(cxlr, cxled, 0);> + up_read(&cxl_dpa_rwsem);
> +> + if (rc)
> + goto err;
scoped_guard(rwsem_read, &cxl_dpa_rwsem) {
rc = cxl_region_attach(cxlr, cxled, 0);
if (rc)
goto err;
}
> +
> + rc = cxl_region_decode_commit(cxlr);
> + if (rc)
> + goto err;
> +
> + p->state = CXL_CONFIG_COMMIT;
> +
> + return cxlr;
> +err:
> + drop_region(cxlr);
> + return ERR_PTR(rc);
> +}
> +
> +/**
> + * cxl_create_region - Establish a region given an endpoint decoder
> + * @cxlrd: root decoder to allocate HPA
> + * @cxled: endpoint decoder 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;
scoped_guard(mutex, &cxlrd->range_lock) {
cxlr = __construct_new_region(cxlrd, cxled, ways);
if (IS_ERR(cxlr))
return cxlr;
}
DJ
> +
> + 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");
> +
> int cxl_add_to_region(struct cxl_port *root, struct cxl_endpoint_decoder *cxled)
> {
> struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> index d2bfd1ff5492..f352f2b1c481 100644
> --- a/drivers/cxl/port.c
> +++ b/drivers/cxl/port.c
> @@ -33,6 +33,7 @@ static void schedule_detach(void *cxlmd)
> static int discover_region(struct device *dev, void *root)
> {
> struct cxl_endpoint_decoder *cxled;
> + struct cxl_memdev *cxlmd;
> int rc;
>
> if (!is_endpoint_decoder(dev))
> @@ -42,7 +43,9 @@ static int discover_region(struct device *dev, void *root)
> 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 22061646b147..133d6db3a70a 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h
> @@ -261,4 +261,8 @@ struct cxl_endpoint_decoder *cxl_request_dpa(struct cxl_memdev *cxlmd,
> bool is_ram,
> 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);
> +
> +int cxl_accel_region_detach(struct cxl_endpoint_decoder *cxled);
> #endif
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