linux-kernel - Re: [PATCH 2/8] cxl/memfeature: Add CXL memory device patrol scrub control feature

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Message-ID: <Z8tOrqOnkv-ZUsEy@aschofie-mobl2.lan>
Date: Fri, 7 Mar 2025 11:53:18 -0800
From: Alison Schofield <alison.schofield@...el.com>
To: shiju.jose@...wei.com
Cc: linux-cxl@...r.kernel.org, dan.j.williams@...el.com, dave@...olabs.net,
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Subject: Re: [PATCH 2/8] cxl/memfeature: Add CXL memory device patrol scrub
 control feature

On Thu, Feb 27, 2025 at 10:38:09PM +0000, shiju.jose@...wei.com wrote:
> From: Shiju Jose <shiju.jose@...wei.com>

snip

> 
> +static int cxl_ps_get_attrs(struct cxl_patrol_scrub_context *cxl_ps_ctx,
> +			    struct cxl_memdev_ps_params *params)
> +{
> +	struct cxl_mailbox *cxl_mbox;
> +	struct cxl_memdev *cxlmd;
> +	u16 min_scrub_cycle = 0;
> +	int i, ret;
> +
> +	if (cxl_ps_ctx->cxlr) {
> +		struct cxl_region *cxlr = cxl_ps_ctx->cxlr;
> +		struct cxl_region_params *p = &cxlr->params;
> +
> +		ret = cxl_hold_region_and_dpa();
> +		if (ret)
> +			return ret;
> +		for (i = p->interleave_ways - 1; i >= 0; i--) {
> +			struct cxl_endpoint_decoder *cxled = p->targets[i];
> +

Hi Shiju,

Although not functionally wrong, the above for loop caught my eye.

p->nr_targets is a better loop initializer when walking p->targets[]
(at this point nr_targets better equal interleave ways but lets use
the count intended for the array being walked)

Is there a reason to walk in reverse? This seems clearer:
for (i = 0; i < p->nr_targets; i++)

The same for loop header repeats below in:
cxl_ps_set_attrs()
cxl_region_scrub_init()
If you change for one, change for all.

snip

> +static int cxl_memdev_scrub_init(struct cxl_memdev *cxlmd,
> +				 struct edac_dev_feature *ras_feature, u8 scrub_inst)
> +{
> +	struct cxl_patrol_scrub_context *cxl_ps_ctx;
> +	struct cxl_feat_entry *feat_entry;
> +
> +	feat_entry = cxl_get_feature_entry(cxlmd->cxlds, &CXL_FEAT_PATROL_SCRUB_UUID);
> +	if (IS_ERR(feat_entry))
> +		return -EOPNOTSUPP;
> +

Along w patch 1 comment, perhaps just check for (!feat_entry) here 
and in a couple of other places below.

snip

>