Re: [PATCH] cxl/acpi: Fix load failures due to single window creation failure

[Dan Williams <dan.j.williams@intel.com>]

Jonathan Cameron wrote:
> On Sat, 17 Feb 2024 12:29:32 -0800
> Dan Williams <dan.j.williams@intel.com> wrote:
> 
> > The expectation is that cxl_parse_cfwms() continues in the face the of
> > failure as evidenced by code like:
> > 
> >     cxlrd = cxl_root_decoder_alloc(root_port, ways, cxl_calc_hb);
> >     if (IS_ERR(cxlrd))
> >     	return 0;
> > 
> > There are other error paths in that function which mistakenly follow
> > idiomatic expectations and return an error when they should not. Most of
> > those mistakes are innocuous checks that hardly ever fail in practice.
> > However, a recent change succeed in making the implementation more
> > fragile by applying an idiomatic, but still wrong "fix" [1]. In this
> > failure case the kernel reports:
> > 
> >     cxl root0: Failed to populate active decoder targets
> >     cxl_acpi ACPI0017:00: Failed to add decode range: [mem 0x00000000-0x7fffffff flags 0x200]
> > 
> > ...which is a real issue with that one window (to be fixed separately),
> > but ends up failing the entirety of cxl_acpi_probe().
> > 
> > Undo that recent breakage while also removing the confusion about
> > ignoring errors. Update all exits paths to return an error per typical
> > expectations and let an outer wrapper function handle dropping the
> > error.
> > 
> > Fixes: 91019b5bc7c2 ("cxl/acpi: Return 'rc' instead of '0' in cxl_parse_cfmws()") [1]
> > Cc: <stable@vger.kernel.org>
> > Cc: Breno Leitao <leitao@debian.org>
> > Cc: Alison Schofield <alison.schofield@intel.com>
> > Cc: Vishal Verma <vishal.l.verma@intel.com>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> 
> General idea makes a lot of sense to me.
> 
> A few comments on specific implementation inline
> 
> > ---
> >  drivers/cxl/acpi.c |   45 +++++++++++++++++++++++++++------------------
> >  1 file changed, 27 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> > index dcf2b39e1048..53d2dff0c7a3 100644
> > --- a/drivers/cxl/acpi.c
> > +++ b/drivers/cxl/acpi.c
> > @@ -316,31 +316,27 @@ static const struct cxl_root_ops acpi_root_ops = {
> >  	.qos_class = cxl_acpi_qos_class,
> >  };
> >  
> > -static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> > -			   const unsigned long end)
> > +static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
> > +			     struct cxl_cfmws_context *ctx)
> >  {
> >  	int target_map[CXL_DECODER_MAX_INTERLEAVE];
> > -	struct cxl_cfmws_context *ctx = arg;
> >  	struct cxl_port *root_port = ctx->root_port;
> >  	struct resource *cxl_res = ctx->cxl_res;
> >  	struct cxl_cxims_context cxims_ctx;
> >  	struct cxl_root_decoder *cxlrd;
> >  	struct device *dev = ctx->dev;
> > -	struct acpi_cedt_cfmws *cfmws;
> >  	cxl_calc_hb_fn cxl_calc_hb;
> >  	struct cxl_decoder *cxld;
> >  	unsigned int ways, i, ig;
> >  	struct resource *res;
> >  	int rc;
> >  
> > -	cfmws = (struct acpi_cedt_cfmws *) header;
> > -
> >  	rc = cxl_acpi_cfmws_verify(dev, cfmws);
> >  	if (rc) {
> >  		dev_err(dev, "CFMWS range %#llx-%#llx not registered\n",
> >  			cfmws->base_hpa,
> >  			cfmws->base_hpa + cfmws->window_size - 1);
> 
> Why keep this error print?

True, that can go.

> > -		return 0;
> > +		return rc;
> >  	}
> >  
> >  	rc = eiw_to_ways(cfmws->interleave_ways, &ways);
> > @@ -376,7 +372,7 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> >  
> >  	cxlrd = cxl_root_decoder_alloc(root_port, ways, cxl_calc_hb);
> >  	if (IS_ERR(cxlrd))
> > -		return 0;
> > +		return PTR_ERR(cxlrd);
> >  
> >  	cxld = &cxlrd->cxlsd.cxld;
> >  	cxld->flags = cfmws_to_decoder_flags(cfmws->restrictions);
> > @@ -420,16 +416,7 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> >  		put_device(&cxld->dev);
> >  	else
> >  		rc = cxl_decoder_autoremove(dev, cxld);
> > -	if (rc) {
> > -		dev_err(dev, "Failed to add decode range: %pr", res);
> > -		return rc;
> 
> As no longer sharing this message. Might be neater to have this lot as
> 	rc = cxl_decoder_add(cxld, target_map);
> err_xormap:
> 	if (rc) {
> 		put_device(&cxld->dev);
> 		return rc;
> 	}
> 
> 	return cxl_decoder_autoremove(dev, cxld);
> 
> or a second error exit path.
> 
> 	rc = cxl_decoder_add(cxld, target_map);
> 	if (rc)
> 		goto err_put_devie;
> 
> 	return cxl_decoder_autoremove(dev, cxld;
> 
> err_put_device;
> 	put_device(&cxld->dev);
> 	return rc;
> 
> err_insert:
> 	kfree(res->name); ...

True, there's enough here to do an even deeper cleanup... below.

> 
> 
> > -	}
> > -	dev_dbg(dev, "add: %s node: %d range [%#llx - %#llx]\n",
> > -		dev_name(&cxld->dev),
> > -		phys_to_target_node(cxld->hpa_range.start),
> > -		cxld->hpa_range.start, cxld->hpa_range.end);
> > -
> > -	return 0;
> > +	return rc;
> >  
> >  err_insert:
> >  	kfree(res->name);
> > @@ -438,6 +425,28 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> >  	return -ENOMEM;
> >  }
> >  
> > +static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
> > +			   const unsigned long end)
> > +{
> > +	struct acpi_cedt_cfmws *cfmws = (struct acpi_cedt_cfmws *)header;
> > +	struct cxl_cfmws_context *ctx = arg;
> > +	struct device *dev = ctx->dev;
> > +	int rc;
> > +
> > +	dev_dbg(dev, "decode range: node: %d range [%#llx - %#llx]\n",
> > +		phys_to_target_node(cfmws->base_hpa), cfmws->base_hpa,
> > +		cfmws->base_hpa + cfmws->window_size - 1);
> 
> Could maybe put this in an else below?
> 
> > +	rc = __cxl_parse_cfmws(cfmws, ctx);
> > +	if (rc)
> > +		dev_err(dev,
> > +			"Failed to add decode range: [%#llx - %#llx] (%d)\n",
> > +			cfmws->base_hpa,
> > +			cfmws->base_hpa + cfmws->window_size - 1, rc);
> > +
> else 
> 	dev_dbg();
> 
> so we only give the dbg version on success?

Yeah, I will switch to this since the previous state was also skipping
the debug messages on success.

Follow-on cleanup:

-- 8< --
From e30c267c0b69d5e4531d8f65ec86e4fa32d72340 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Tue, 20 Feb 2024 22:44:34 -0800
Subject: [PATCH] cxl/acpi: Cleanup __cxl_parse_cfmws() error exits

As a follow on to the recent rework of __cxl_parse_cfmws() to always
return errors, use cleanup.h helpers to remove goto and other cleanups
now that logging is moved to the cxl_parse_cfmws() wrapper.

Reported-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Closes: http://lore.kernel.org/r/20240219124041.00002bda@Huawei.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/acpi.c | 45 +++++++++++++++++++--------------------------
 1 file changed, 19 insertions(+), 26 deletions(-)

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index 1a3e6aafbdcc..b1ea2d152c65 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -319,25 +319,23 @@ static const struct cxl_root_ops acpi_root_ops = {
 static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
 			     struct cxl_cfmws_context *ctx)
 {
+	struct device *cxld_dev __free(put_device) = NULL;
 	int target_map[CXL_DECODER_MAX_INTERLEAVE];
 	struct cxl_port *root_port = ctx->root_port;
+	struct resource *res __free(kfree) = NULL;
 	struct resource *cxl_res = ctx->cxl_res;
+	const char *name __free(kfree) = NULL;
 	struct cxl_cxims_context cxims_ctx;
 	struct cxl_root_decoder *cxlrd;
 	struct device *dev = ctx->dev;
 	cxl_calc_hb_fn cxl_calc_hb;
 	struct cxl_decoder *cxld;
 	unsigned int ways, i, ig;
-	struct resource *res;
 	int rc;
 
 	rc = cxl_acpi_cfmws_verify(dev, cfmws);
-	if (rc) {
-		dev_err(dev, "CFMWS range %#llx-%#llx not registered\n",
-			cfmws->base_hpa,
-			cfmws->base_hpa + cfmws->window_size - 1);
+	if (rc)
 		return rc;
-	}
 
 	rc = eiw_to_ways(cfmws->interleave_ways, &ways);
 	if (rc)
@@ -352,10 +350,11 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
 	if (!res)
 		return -ENOMEM;
 
-	res->name = kasprintf(GFP_KERNEL, "CXL Window %d", ctx->id++);
-	if (!res->name)
-		goto err_name;
+	name = kasprintf(GFP_KERNEL, "CXL Window %d", ctx->id++);
+	if (!name)
+		return -ENOMEM;
 
+	res->name = name;
 	res->start = cfmws->base_hpa;
 	res->end = cfmws->base_hpa + cfmws->window_size - 1;
 	res->flags = IORESOURCE_MEM;
@@ -363,7 +362,9 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
 	/* add to the local resource tracking to establish a sort order */
 	rc = insert_resource(cxl_res, res);
 	if (rc)
-		goto err_insert;
+		return rc;
+	name = NULL;
+	res = NULL;
 
 	if (cfmws->interleave_arithmetic == ACPI_CEDT_CFMWS_ARITHMETIC_MODULO)
 		cxl_calc_hb = cxl_hb_modulo;
@@ -375,11 +376,12 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
 		return PTR_ERR(cxlrd);
 
 	cxld = &cxlrd->cxlsd.cxld;
+	cxld_dev = &cxld->dev;
 	cxld->flags = cfmws_to_decoder_flags(cfmws->restrictions);
 	cxld->target_type = CXL_DECODER_HOSTONLYMEM;
 	cxld->hpa_range = (struct range) {
-		.start = res->start,
-		.end = res->end,
+		.start = cfmws->base_hpa,
+		.end = cfmws->base_hpa + cfmws->window_size - 1,
 	};
 	cxld->interleave_ways = ways;
 	/*
@@ -399,11 +401,10 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
 			rc = acpi_table_parse_cedt(ACPI_CEDT_TYPE_CXIMS,
 						   cxl_parse_cxims, &cxims_ctx);
 			if (rc < 0)
-				goto err_xormap;
+				return rc;
 			if (!cxlrd->platform_data) {
 				dev_err(dev, "No CXIMS for HBIG %u\n", ig);
-				rc = -EINVAL;
-				goto err_xormap;
+				return -EINVAL;
 			}
 		}
 	}
@@ -411,18 +412,10 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
 	cxlrd->qos_class = cfmws->qtg_id;
 
 	rc = cxl_decoder_add(cxld, target_map);
-err_xormap:
 	if (rc)
-		put_device(&cxld->dev);
-	else
-		rc = cxl_decoder_autoremove(dev, cxld);
-	return rc;
-
-err_insert:
-	kfree(res->name);
-err_name:
-	kfree(res);
-	return -ENOMEM;
+		return rc;
+	cxld_dev = NULL;
+	return cxl_decoder_autoremove(dev, cxld);
 }
 
 static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
-- 
2.43.0