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Message-ID: <20250623104302.00004405@huawei.com>
Date: Mon, 23 Jun 2025 10:43:02 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Neeraj Kumar <s.neeraj@...sung.com>
CC: <dan.j.williams@...el.com>, <dave@...olabs.net>, <dave.jiang@...el.com>,
<alison.schofield@...el.com>, <vishal.l.verma@...el.com>,
<ira.weiny@...el.com>, <a.manzanares@...sung.com>, <nifan.cxl@...il.com>,
<anisa.su@...sung.com>, <vishak.g@...sung.com>, <krish.reddy@...sung.com>,
<arun.george@...sung.com>, <alok.rathore@...sung.com>,
<neeraj.kernel@...il.com>, <linux-kernel@...r.kernel.org>,
<linux-cxl@...r.kernel.org>, <nvdimm@...ts.linux.dev>,
<gost.dev@...sung.com>, <cpgs@...sung.com>
Subject: Re: [RFC PATCH 14/20] cxl/region: Add cxl pmem region creation
routine for region persistency
On Tue, 17 Jun 2025 18:09:38 +0530
Neeraj Kumar <s.neeraj@...sung.com> wrote:
> Added exported cxl_create_pmem_region routine to create cxl pmem region
For function names always add () after and drop 'function/routine' etc.
Ends up shorter and easier to read.
> from LSA parsed cxl region information.
> Inspirition for the function is taken from ndctl device attribute
> (_store) call. It allocates cxlr and fills information parsed from LSA
> and calls device_add(&cxlr->dev) to initiates further region creation
> porbes
Spell check.
>
> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
> ---
> drivers/cxl/core/port.c | 6 ++
> drivers/cxl/core/region.c | 208 ++++++++++++++++++++++++++++++++++++++
> drivers/cxl/cxl.h | 11 ++
> 3 files changed, 225 insertions(+)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index b98b1ccffd1c..8990e3c3474d 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2522,6 +2522,214 @@ static ssize_t create_ram_region_show(struct device *dev,
> return __create_region_show(to_cxl_root_decoder(dev), buf);
> }
>
> +static ssize_t update_region_size(struct cxl_region *cxlr, u64 val)
> +{
> + int rc;
> +
> + rc = down_write_killable(&cxl_region_rwsem);
ACQUIRE() as mentioned below.
> + if (rc)
> + return rc;
> +
> + if (val)
> + rc = alloc_hpa(cxlr, val);
> + else
> + rc = free_hpa(cxlr);
> + up_write(&cxl_region_rwsem);
> +
> + if (rc)
> + return rc;
return rc;
> +
> + return 0;
> +}
> +
> +static ssize_t update_region_dpa_size(struct cxl_region *cxlr,
> + struct cxl_decoder *cxld,
> + unsigned long long size)
> +{
> + int rc;
> + struct cxl_endpoint_decoder *cxled =
> + to_cxl_endpoint_decoder(&cxld->dev);
> +
> + if (!IS_ALIGNED(size, SZ_256M))
> + return -EINVAL;
> +
> + rc = cxl_dpa_free(cxled);
> + if (rc)
> + return rc;
> +
> + if (size == 0)
> + return 0;
> +
> + rc = cxl_dpa_alloc(cxled, size);
return cxl_dpa_alloc()
Unless something more is getting added here in later patches in which case
you can ignore this comment.
> + if (rc)
> + return rc;
> +
> + return 0;
> +}
> +
> +static ssize_t update_region_dpa_mode(struct cxl_region *cxlr,
> + struct cxl_decoder *cxld)
> +{
> + int rc;
> + struct cxl_endpoint_decoder *cxled =
> + to_cxl_endpoint_decoder(&cxld->dev);
Maybe don't bother with local variable and just put this
below as the parameter.
> +
> + rc = cxl_dpa_set_mode(cxled, CXL_DECODER_PMEM);
return cxl_dpa_set_mode()
> + if (rc)
> + return rc;
> +
> + return 0;
> +}
> +
> +static size_t attach_region_target(struct cxl_region *cxlr,
> + struct cxl_decoder *cxld, int pos)
> +{
> + int rc;
> + struct cxl_endpoint_decoder *cxled =
> + to_cxl_endpoint_decoder(&cxld->dev);
> +
> + rc = attach_target(cxlr, cxled, pos, TASK_INTERRUPTIBLE);
> +
No blank line here
> + if (rc < 0)
Can it ever be > 0 ?
If not, return attach_target() should be fine.
> + return rc;
> +
> + return 0;
> +}
> +
> +static ssize_t commit_region(struct cxl_region *cxlr)
> +{
> + struct cxl_region_params *p = &cxlr->params;
> + ssize_t rc;
> +
> + rc = down_write_killable(&cxl_region_rwsem);
Maybe look at Dan's new ACQUIRE() series. The last patch in there
is targeting code similar to this.
> + if (rc)
> + return rc;
> +
> + /* Already in the requested state? */
> + if (p->state >= CXL_CONFIG_COMMIT)
> + goto out;
> +
> + /* Not ready to commit? */
> + if (p->state < CXL_CONFIG_ACTIVE) {
> + rc = -ENXIO;
> + goto out;
> + }
> +
> + /*
> + * Invalidate caches before region setup to drop any speculative
> + * consumption of this address space
> + */
> + rc = cxl_region_invalidate_memregion(cxlr);
> + if (rc)
> + goto out;
> +
> + rc = cxl_region_decode_commit(cxlr);
> + if (rc == 0)
With AQUIRE() stuff you can just do
if (rc)
return rc;
here
> + p->state = CXL_CONFIG_COMMIT;
> +out:
> + up_write(&cxl_region_rwsem);
> + if (rc)
> + return rc;
> + return 0;
> +}
> +
> +static struct cxl_region *
> +devm_cxl_pmem_add_region(struct cxl_root_decoder *cxlrd,
> + struct cxl_decoder *cxld,
> + struct cxl_pmem_region_params *params, int id,
> + enum cxl_decoder_mode mode, enum cxl_decoder_type type)
> +{
> + struct cxl_port *port;
> + struct cxl_region *cxlr;
> + struct cxl_region_params *p;
> + struct device *dev;
> + int rc;
> +
> + if (!cxlrd)
> + return ERR_PTR(-EINVAL);
For a check like this, add a comment on why it might be NULL.
If it can't be, then drop the check.
> +
> + port = to_cxl_port(cxlrd->cxlsd.cxld.dev.parent);
Maybe add a comment on which port this actually is. These long indirections
can make that hard to figure out!
> +
> + cxlr = cxl_region_alloc(cxlrd, id);
> + if (IS_ERR(cxlr))
> + return cxlr;
> + cxlr->mode = mode;
> + cxlr->type = type;
> +
> + dev = &cxlr->dev;
> + rc = dev_set_name(dev, "region%d", id);
> + if (rc)
> + goto err;
> +
> + p = &cxlr->params;
> + p->uuid = params->uuid;
> + p->interleave_ways = params->nlabel;
> + p->interleave_granularity = params->ig;
> +
> + /* Update region size */
> + if (update_region_size(cxlr, params->rawsize))
> + goto err;
> +
> + /* Flush cxl wq */
Much more useful to say 'why' you are flushing it. It's obvious
from the code that you are.
> + cxl_wq_flush();
> +
> + /* Clear DPA Size */
I'd look at all these comments and where they are obvious, drop the comment
and let the code speak for itself.
> + if (update_region_dpa_size(cxlr, cxld, 0))
> + goto err;
> +
> + /* Update DPA mode */
> + if (update_region_dpa_mode(cxlr, cxld))
> + goto err;
> +
> + /* Update DPA Size */
> + if (update_region_dpa_size(cxlr, cxld, params->rawsize))
> + goto err;
> +
> + /* Attach region targets */
It's attaching just one by the look of it. I'd just drop the comment.
> + if (attach_region_target(cxlr, cxld, params->position))
> + goto err;
> +
> + /* Commit Region */
> + if (commit_region(cxlr))
> + goto err;
> +
> + rc = device_add(dev);
> + if (rc)
> + goto err;
> +
> + rc = devm_add_action_or_reset(port->uport_dev, unregister_region, cxlr);
> + if (rc)
> + return ERR_PTR(rc);
> +
> + dev_dbg(port->uport_dev, "%s: created %s\n",
> + dev_name(&cxlrd->cxlsd.cxld.dev), dev_name(dev));
> + return cxlr;
> +
> +err:
> + put_device(dev);
> + return ERR_PTR(rc);
> +}
> +
> +struct cxl_region *cxl_create_pmem_region(struct cxl_root_decoder *cxlrd,
> + struct cxl_decoder *cxld,
> + struct cxl_pmem_region_params *params, int id)
> +{
> + int rc;
> +
> + rc = memregion_alloc(GFP_KERNEL);
> + if (rc < 0)
> + return ERR_PTR(rc);
> +
> + if (atomic_cmpxchg(&cxlrd->region_id, id, rc) != id) {
> + memregion_free(rc);
> + return ERR_PTR(-EBUSY);
> + }
I'm a little surprised not to see cleanup of the memregion via
devm somewhere here.
> +
> + return devm_cxl_pmem_add_region(cxlrd, cxld, params, id,
> + CXL_DECODER_PMEM, CXL_DECODER_HOSTONLYMEM);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_create_pmem_region, "CXL");
> +
> static struct cxl_region *__create_region(struct cxl_root_decoder *cxlrd,
> enum cxl_decoder_mode mode, int id)
> {
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