linux-kernel - Re: [PATCH v3 09/25] cxl/hdm: Add dynamic capacity size support to endpoint decoders

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Message-ID: <66c7f3624d881_1719d2943b@iweiny-mobl.notmuch>
Date: Thu, 22 Aug 2024 21:26:42 -0500
From: Ira Weiny <ira.weiny@...el.com>
To: Dave Jiang <dave.jiang@...el.com>, <ira.weiny@...el.com>, Fan Ni
	<fan.ni@...sung.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	"Navneet Singh" <navneet.singh@...el.com>, Chris Mason <clm@...com>, Josef
 Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>, Petr Mladek
	<pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, Andy Shevchenko
	<andriy.shevchenko@...ux.intel.com>, Rasmus Villemoes
	<linux@...musvillemoes.dk>, Sergey Senozhatsky <senozhatsky@...omium.org>,
	Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>
CC: Dan Williams <dan.j.williams@...el.com>, Davidlohr Bueso
	<dave@...olabs.net>, Alison Schofield <alison.schofield@...el.com>, "Vishal
 Verma" <vishal.l.verma@...el.com>, <linux-btrfs@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <nvdimm@...ts.linux.dev>
Subject: Re: [PATCH v3 09/25] cxl/hdm: Add dynamic capacity size support to
 endpoint decoders

Dave Jiang wrote:
> 
> 
> On 8/16/24 7:44 AM, ira.weiny@...el.com wrote:
> > From: Navneet Singh <navneet.singh@...el.com>
> > 

[snip]

> > +static int dc_mode_to_region_index(enum cxl_decoder_mode mode)
> > +{
> > +	return mode - CXL_DECODER_DC0;
> > +}
> > +
> > +static int cxl_request_skip(struct cxl_endpoint_decoder *cxled,
> > +			    resource_size_t skip_base, resource_size_t skip_len)
> > +{
> > +	struct cxl_dev_state *cxlds = cxled_to_memdev(cxled)->cxlds;
> > +	const char *name = dev_name(&cxled->cxld.dev);
> > +	struct cxl_port *port = cxled_to_port(cxled);
> > +	struct resource *dpa_res = &cxlds->dpa_res;
> > +	struct device *dev = &port->dev;
> > +	struct resource *res;
> > +	int rc;
> > +
> > +	res = __request_region(dpa_res, skip_base, skip_len, name, 0);
> > +	if (!res)
> > +		return -EBUSY;
> > +
> > +	rc = xa_insert(&cxled->skip_res, skip_base, res, GFP_KERNEL);
> 
> Maybe rename skip_res to skip_xa, given most of the vars in CXL with
> _res are 'struct resource' to avoid confusion. See 'dpa_res' above.
> 

Good idea.
[done]

> > +	if (rc) {
> > +		__release_region(dpa_res, skip_base, skip_len);
> > +		return rc;
> > +	}
> > +
> > +	dev_dbg(dev, "decoder%d.%d: skipped space; %pr\n",
> > +		port->id, cxled->cxld.id, res);
> > +	return 0;
> > +}
> > +
> > +static int cxl_reserve_dpa_skip(struct cxl_endpoint_decoder *cxled,
> > +				resource_size_t base, resource_size_t skipped)
> > +{
> > +	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> > +	struct cxl_port *port = cxled_to_port(cxled);
> > +	struct cxl_dev_state *cxlds = cxlmd->cxlds;
> > +	resource_size_t skip_base = base - skipped;
> > +	struct device *dev = &port->dev;
> > +	resource_size_t skip_len = 0;
> > +	int rc, index;
> > +
> > +	if (resource_size(&cxlds->ram_res) && skip_base <= cxlds->ram_res.end) {
> > +		skip_len = cxlds->ram_res.end - skip_base + 1;
> > +		rc = cxl_request_skip(cxled, skip_base, skip_len);
> > +		if (rc)
> > +			return rc;
> > +		skip_base += skip_len;
> > +	}
> > +
> > +	if (skip_base == base) {
> > +		dev_dbg(dev, "skip done ram!\n");
> > +		return 0;
> > +	}
> > +
> > +	if (resource_size(&cxlds->pmem_res) &&
> > +	    skip_base <= cxlds->pmem_res.end) {
> > +		skip_len = cxlds->pmem_res.end - skip_base + 1;
> > +		rc = cxl_request_skip(cxled, skip_base, skip_len);
> > +		if (rc)
> > +			return rc;
> > +		skip_base += skip_len;
> > +	}
> 
> Does 'skip_base == base' need to be checked here again before going to DCD?

No it is checked below...

> 
> DJ
> 
> > +
> > +	index = dc_mode_to_region_index(cxled->mode);
> > +	for (int i = 0; i <= index; i++) {
> > +		struct resource *dcr = &cxlds->dc_res[i];
> > +
> > +		if (skip_base < dcr->start) {
> > +			skip_len = dcr->start - skip_base;
> > +			rc = cxl_request_skip(cxled, skip_base, skip_len);
> > +			if (rc)
> > +				return rc;
> > +			skip_base += skip_len;
> > +		}
> > +
> > +		if (skip_base == base) {
> > +			dev_dbg(dev, "skip done DC region %d!\n", i);
> > +			break;
> > +		}

... here.

After any skips between pmem and the first DC partition.
Ira

> > +
> > +		if (resource_size(dcr) && skip_base <= dcr->end) {
> > +			if (skip_base > base) {
> > +				dev_err(dev, "Skip error DC region %d; skip_base %pa; base %pa\n",
> > +					i, &skip_base, &base);
> > +				return -ENXIO;
> > +			}
> > +
> > +			skip_len = dcr->end - skip_base + 1;
> > +			rc = cxl_request_skip(cxled, skip_base, skip_len);
> > +			if (rc)
> > +				return rc;
> > +			skip_base += skip_len;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +

[snip]