[PATCH v2] cxl/region: Add dev_dbg() detail on failure to allocate HPA space

[PATCH v2] cxl/region: Add dev_dbg() detail on failure to allocate HPA space

[alison.schofield]

From: Alison Schofield <alison.schofield@intel.com>

When the region driver fails while allocating HPA space for a
new region it can be because the parent resource, the CXL Window,
has no more available space.

In that case, the debug user sees this message:
cxl_core:alloc_hpa:555: cxl region2: failed to allocate HPA: -34

Expand the message like this:
cxl_core:alloc_hpa:555: cxl region8: HPA allocation error:-34 for size:0x20000000 in CXL Window 0 [mem 0xf010000000-0xf04fffffff flags 0x200]

Now the debug user can examine /proc/iomem and consider actions
like removing other allocations in that space or reducing the
size of their region request.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
---

Changes in v2:
- Improve the message text (Vishal)
- Add reviewed by tags (DaveJ, Vishal)
- Link to v1:
https://lore.kernel.org/linux-cxl/20231114040147.1124696-1-alison.schofield@intel.com/


 drivers/cxl/core/region.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 56e575c79bb4..ec792af873c4 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -552,8 +552,9 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
 	res = alloc_free_mem_region(cxlrd->res, size, SZ_256M,
 				    dev_name(&cxlr->dev));
 	if (IS_ERR(res)) {
-		dev_dbg(&cxlr->dev, "failed to allocate HPA: %ld\n",
-			PTR_ERR(res));
+		dev_dbg(&cxlr->dev,
+			"HPA allocation error:%ld for size:%#llx in %s %pr\n",
+			PTR_ERR(res), size, cxlrd->res->name, cxlrd->res);
 		return PTR_ERR(res);
 	}
 

base-commit: b85ea95d086471afb4ad062012a4d73cd328fa86
-- 
2.37.3

RE: [PATCH v2] cxl/region: Add dev_dbg() detail on failure to allocate HPA space

[Dan Williams]

alison.schofield@ wrote:
> From: Alison Schofield <alison.schofield@intel.com>
> 
> When the region driver fails while allocating HPA space for a
> new region it can be because the parent resource, the CXL Window,
> has no more available space.
> 
> In that case, the debug user sees this message:
> cxl_core:alloc_hpa:555: cxl region2: failed to allocate HPA: -34
> 
> Expand the message like this:
> cxl_core:alloc_hpa:555: cxl region8: HPA allocation error:-34 for size:0x20000000 in CXL Window 0 [mem 0xf010000000-0xf04fffffff flags 0x200]
> 
> Now the debug user can examine /proc/iomem and consider actions
> like removing other allocations in that space or reducing the
> size of their region request.
> 
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
> 
> Changes in v2:
> - Improve the message text (Vishal)
> - Add reviewed by tags (DaveJ, Vishal)
> - Link to v1:
> https://lore.kernel.org/linux-cxl/20231114040147.1124696-1-alison.schofield@intel.com/
> 
> 
>  drivers/cxl/core/region.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 56e575c79bb4..ec792af873c4 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -552,8 +552,9 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
>  	res = alloc_free_mem_region(cxlrd->res, size, SZ_256M,
>  				    dev_name(&cxlr->dev));
>  	if (IS_ERR(res)) {
> -		dev_dbg(&cxlr->dev, "failed to allocate HPA: %ld\n",
> -			PTR_ERR(res));
> +		dev_dbg(&cxlr->dev,
> +			"HPA allocation error:%ld for size:%#llx in %s %pr\n",
> +			PTR_ERR(res), size, cxlrd->res->name, cxlrd->res);

I notice that this did not pick up Vishal's suggested "error (%d) ..."
style for conveying the error code.

   "HPA allocation error (%d) for size: %llx in %s ..."

I prefer that style as well.

Re: [PATCH v2] cxl/region: Add dev_dbg() detail on failure to allocate HPA space

[Alison Schofield]

On Mon, Dec 04, 2023 at 05:46:26PM -0800, Dan Williams wrote:
> alison.schofield@ wrote:
> > From: Alison Schofield <alison.schofield@intel.com>

snip

> > 
> > 
> > Changes in v2:
> > - Improve the message text (Vishal)
> > - Add reviewed by tags (DaveJ, Vishal)
> > - Link to v1:
> > https://lore.kernel.org/linux-cxl/20231114040147.1124696-1-alison.schofield@intel.com/
> > 
> > 
> >  drivers/cxl/core/region.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index 56e575c79bb4..ec792af873c4 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -552,8 +552,9 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
> >  	res = alloc_free_mem_region(cxlrd->res, size, SZ_256M,
> >  				    dev_name(&cxlr->dev));
> >  	if (IS_ERR(res)) {
> > -		dev_dbg(&cxlr->dev, "failed to allocate HPA: %ld\n",
> > -			PTR_ERR(res));
> > +		dev_dbg(&cxlr->dev,
> > +			"HPA allocation error:%ld for size:%#llx in %s %pr\n",
> > +			PTR_ERR(res), size, cxlrd->res->name, cxlrd->res);
> 
> I notice that this did not pick up Vishal's suggested "error (%d) ..."
> style for conveying the error code.
> 
>    "HPA allocation error (%d) for size: %llx in %s ..."
> 
> I prefer that style as well.

I should have said something in the changelog. I rejected the
parentheses based on this: 

"Printing numbers in parentheses (%d) adds no value and should be
avoided."  in Documentation/process/coding-style.rst

Since it's a dev_dbg() msg I'll go ahead and add those parens.
(But this is not a precedent for parens all over ;))

Alison