[PATCH v2 0/2] cxl/region: Improve Soft Reserved resource handling

[PATCH v2 0/2] cxl/region: Improve Soft Reserved resource handling

[alison.schofield]

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

Changes in v2:
- Rebase to 6.5-rc1

v1: https://lore.kernel.org/linux-cxl/cover.1687568084.git.alison.schofield@intel.com/


Make the cxl/region driver handle these 2 observed scenarios:

1) Soft reserved resources were observed as sometimes being the parent
and sometimes being the child of a region resource. Patch 1 clears up
that inconsistency.

2) Soft reserved resources were also observed as stranded after region 
teardown, making the address space the region released unavailable for
reallocation. Patch 2 implements soft reserved resource removal.

Alison Schofield (2):
  cxl/region: Try to add a region resource to a soft reserved parent
  cxl/region: Remove a soft reserved resource at region teardown

 drivers/cxl/core/region.c | 164 +++++++++++++++++++++++++++++++++++---
 1 file changed, 153 insertions(+), 11 deletions(-)


base-commit: 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5
-- 
2.37.3

[PATCH v2 1/2] cxl/region: Try to add a region resource to a soft reserved parent

[alison.schofield]

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

During region autodiscovery, the region driver always inserts the
region resource as a child of the root decoder, a CXL WINDOW. It
has the effect of making a soft reserved resource, with an exactly
matching address range, a child of the region resource.

It looks like this in /proc/iomem:

2080000000-29dbfffffff : CXL Window 0
  2080000000-247fffffff : region0
    2080000000-247fffffff : Soft Reserved

Search for soft reserved resources that include the region resource,
and add the new region resource as a child of that found resource.
If a soft reserved resource is not found, insert to the root decoder
as usual.

With this change, it looks like this:

2080000000-29dbfffffff : CXL Window 0
  2080000000-247fffffff : Soft Reserved
    2080000000-247fffffff : region0

This odd parenting only occurs when the resources are an exact match.
When the region resource only uses part of a soft reserved resource,
the parenting appears more logical like this:

2080000000-29dbfffffff : CXL Window 0
  2080000000-287fffffff : Soft Reserved
    2080000000-247fffffff : region0

Aside from the more logical appearance, this change is in preparation
for further cleanup in region teardown. A follow-on patch intends to
find and free soft reserved resources upon region teardown.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/core/region.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index e115ba382e04..36c0c0dd5697 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2709,6 +2709,28 @@ static int match_region_by_range(struct device *dev, void *data)
 	return rc;
 }
 
+static int insert_resource_soft_reserved(struct resource *soft_res, void *arg)
+{
+	struct resource *parent, *new, *res = arg;
+	bool found = false;
+
+	parent = soft_res->parent;
+	if (!parent)
+		return 0;
+
+	/* Caller provides a copy of soft_res. Find the actual resource. */
+	for (new = parent->child; new; new = new->sibling) {
+		if (resource_contains(new, soft_res)) {
+			found = true;
+			break;
+		}
+	}
+	if (found)
+		return insert_resource(new, res) == 0;
+
+	return 0;
+}
+
 /* Establish an empty region covering the given HPA range */
 static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
 					   struct cxl_endpoint_decoder *cxled)
@@ -2719,7 +2741,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
 	struct cxl_region_params *p;
 	struct cxl_region *cxlr;
 	struct resource *res;
-	int rc;
+	int rc = 0;
 
 	do {
 		cxlr = __create_region(cxlrd, cxled->mode,
@@ -2755,7 +2777,13 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
 
 	*res = DEFINE_RES_MEM_NAMED(hpa->start, range_len(hpa),
 				    dev_name(&cxlr->dev));
-	rc = insert_resource(cxlrd->res, res);
+
+	/* Try inserting to a Soft Reserved parent, fallback to root decoder */
+	if (walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED, 0,
+				res->start, res->end, res,
+				insert_resource_soft_reserved) != 1)
+		rc = insert_resource(cxlrd->res, res);
+
 	if (rc) {
 		/*
 		 * Platform-firmware may not have split resources like "System
-- 
2.37.3

Re: [PATCH v2 1/2] cxl/region: Try to add a region resource to a soft reserved parent

[Jonathan Cameron]

On Fri,  4 Aug 2023 12:31:39 -0700
alison.schofield@intel.com wrote:

> From: Alison Schofield <alison.schofield@intel.com>
> 
> During region autodiscovery, the region driver always inserts the
> region resource as a child of the root decoder, a CXL WINDOW. It
> has the effect of making a soft reserved resource, with an exactly
> matching address range, a child of the region resource.
> 
> It looks like this in /proc/iomem:
> 
> 2080000000-29dbfffffff : CXL Window 0
>   2080000000-247fffffff : region0
>     2080000000-247fffffff : Soft Reserved
> 
> Search for soft reserved resources that include the region resource,
> and add the new region resource as a child of that found resource.
> If a soft reserved resource is not found, insert to the root decoder
> as usual.
> 
> With this change, it looks like this:
> 
> 2080000000-29dbfffffff : CXL Window 0
>   2080000000-247fffffff : Soft Reserved
>     2080000000-247fffffff : region0
> 
> This odd parenting only occurs when the resources are an exact match.
> When the region resource only uses part of a soft reserved resource,
> the parenting appears more logical like this:
> 
> 2080000000-29dbfffffff : CXL Window 0
>   2080000000-287fffffff : Soft Reserved
>     2080000000-247fffffff : region0
> 
> Aside from the more logical appearance, this change is in preparation
> for further cleanup in region teardown. A follow-on patch intends to
> find and free soft reserved resources upon region teardown.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>

Hi Alison

A comment and a question inline.

Thanks,

Jonathan

> ---
>  drivers/cxl/core/region.c | 32 ++++++++++++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index e115ba382e04..36c0c0dd5697 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2709,6 +2709,28 @@ static int match_region_by_range(struct device *dev, void *data)
>  	return rc;
>  }
>  
> +static int insert_resource_soft_reserved(struct resource *soft_res, void *arg)
> +{
> +	struct resource *parent, *new, *res = arg;
> +	bool found = false;
> +
> +	parent = soft_res->parent;
> +	if (!parent)
> +		return 0;
> +
> +	/* Caller provides a copy of soft_res. Find the actual resource. */
> +	for (new = parent->child; new; new = new->sibling) {
> +		if (resource_contains(new, soft_res)) {
> +			found = true;
> +			break;
> +		}
> +	}
> +	if (found)
> +		return insert_resource(new, res) == 0;

Why not do this in the the if above then directly return there?
Also, should we get an error here, does it make sense to carry on?
(I don't think we can get an error, but if that's the case we shouldn't
 be checking for one)  If it's a corner we aren't sure about, good
to add a comment on what the error case might be and what we are doing
as a result.

> +
> +	return 0;
> +}
> +
>  /* Establish an empty region covering the given HPA range */
>  static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  					   struct cxl_endpoint_decoder *cxled)
> @@ -2719,7 +2741,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  	struct cxl_region_params *p;
>  	struct cxl_region *cxlr;
>  	struct resource *res;
> -	int rc;
> +	int rc = 0;
>  
>  	do {
>  		cxlr = __create_region(cxlrd, cxled->mode,
> @@ -2755,7 +2777,13 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  
>  	*res = DEFINE_RES_MEM_NAMED(hpa->start, range_len(hpa),
>  				    dev_name(&cxlr->dev));
> -	rc = insert_resource(cxlrd->res, res);
> +
> +	/* Try inserting to a Soft Reserved parent, fallback to root decoder */
> +	if (walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED, 0,
> +				res->start, res->end, res,
> +				insert_resource_soft_reserved) != 1)
> +		rc = insert_resource(cxlrd->res, res);
> +
>  	if (rc) {
>  		/*
>  		 * Platform-firmware may not have split resources like "System

Re: [PATCH v2 1/2] cxl/region: Try to add a region resource to a soft reserved parent

[Alison Schofield]

On Mon, Aug 07, 2023 at 03:24:07PM +0100, Jonathan Cameron wrote:
> On Fri,  4 Aug 2023 12:31:39 -0700
> alison.schofield@intel.com wrote:
> 
> > From: Alison Schofield <alison.schofield@intel.com>
> > 
> > During region autodiscovery, the region driver always inserts the
> > region resource as a child of the root decoder, a CXL WINDOW. It
> > has the effect of making a soft reserved resource, with an exactly
> > matching address range, a child of the region resource.
> > 
> > It looks like this in /proc/iomem:
> > 
> > 2080000000-29dbfffffff : CXL Window 0
> >   2080000000-247fffffff : region0
> >     2080000000-247fffffff : Soft Reserved
> > 
> > Search for soft reserved resources that include the region resource,
> > and add the new region resource as a child of that found resource.
> > If a soft reserved resource is not found, insert to the root decoder
> > as usual.
> > 
> > With this change, it looks like this:
> > 
> > 2080000000-29dbfffffff : CXL Window 0
> >   2080000000-247fffffff : Soft Reserved
> >     2080000000-247fffffff : region0
> > 
> > This odd parenting only occurs when the resources are an exact match.
> > When the region resource only uses part of a soft reserved resource,
> > the parenting appears more logical like this:
> > 
> > 2080000000-29dbfffffff : CXL Window 0
> >   2080000000-287fffffff : Soft Reserved
> >     2080000000-247fffffff : region0
> > 
> > Aside from the more logical appearance, this change is in preparation
> > for further cleanup in region teardown. A follow-on patch intends to
> > find and free soft reserved resources upon region teardown.
> > 
> > Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> 
> Hi Alison
> 
> A comment and a question inline.
> 
> Thanks,
> 
> Jonathan
> 
> > ---
> >  drivers/cxl/core/region.c | 32 ++++++++++++++++++++++++++++++--
> >  1 file changed, 30 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index e115ba382e04..36c0c0dd5697 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -2709,6 +2709,28 @@ static int match_region_by_range(struct device *dev, void *data)
> >  	return rc;
> >  }
> >  
> > +static int insert_resource_soft_reserved(struct resource *soft_res, void *arg)
> > +{
> > +	struct resource *parent, *new, *res = arg;
> > +	bool found = false;
> > +
> > +	parent = soft_res->parent;
> > +	if (!parent)
> > +		return 0;
> > +
> > +	/* Caller provides a copy of soft_res. Find the actual resource. */
> > +	for (new = parent->child; new; new = new->sibling) {
> > +		if (resource_contains(new, soft_res)) {
> > +			found = true;
> > +			break;
> > +		}
> > +	}
> > +	if (found)
> > +		return insert_resource(new, res) == 0;
> 

Thanks for the review Jonathan,

> Why not do this in the the if above then directly return there?
That would be better. Thanks.


> Also, should we get an error here, does it make sense to carry on?
> (I don't think we can get an error, but if that's the case we shouldn't
>  be checking for one)  If it's a corner we aren't sure about, good
> to add a comment on what the error case might be and what we are doing
> as a result.'


I see now this is hiding 2 cases in one error return
1) no soft reserved found
2) soft reserved found but failed to insert.

I think it can get an error if firmware set up soft reserved on bad
boundaries.

...scroll down...

> 
> > +
> > +	return 0;
> > +}
> > +
> >  /* Establish an empty region covering the given HPA range */
> >  static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> >  					   struct cxl_endpoint_decoder *cxled)
> > @@ -2719,7 +2741,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> >  	struct cxl_region_params *p;
> >  	struct cxl_region *cxlr;
> >  	struct resource *res;
> > -	int rc;
> > +	int rc = 0;
> >  
> >  	do {
> >  		cxlr = __create_region(cxlrd, cxled->mode,
> > @@ -2755,7 +2777,13 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> >  
> >  	*res = DEFINE_RES_MEM_NAMED(hpa->start, range_len(hpa),
> >  				    dev_name(&cxlr->dev));
> > -	rc = insert_resource(cxlrd->res, res);
> > +
> > +	/* Try inserting to a Soft Reserved parent, fallback to root decoder */
> > +	if (walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED, 0,
> > +				res->start, res->end, res,
> > +				insert_resource_soft_reserved) != 1)
> > +		rc = insert_resource(cxlrd->res, res);
> > +

I'll rework this error handling to not try to insert to root decoder if
insert to soft reserved fails. Only try to insert to root decoder if soft
reserved does not exist.

> >  	if (rc) {
> >  		/*
> >  		 * Platform-firmware may not have split resources like "System
>

I think the insert to soft reserved can fail as describe here:
(Let me show this complete error case above)

	if (rc) {
                /*
                 * Platform-firmware may not have split resources like "System
                 * RAM" on CXL window boundaries see cxl_region_iomem_release()
                 */
                dev_warn(cxlmd->dev.parent,
                         "%s:%s: %s %s cannot insert resource\n",
                         dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
                         __func__, dev_name(&cxlr->dev));
        }

Re: [PATCH v2 1/2] cxl/region: Try to add a region resource to a soft reserved parent

[Dave Jiang]

On 8/4/23 12:31, alison.schofield@intel.com wrote:
> From: Alison Schofield <alison.schofield@intel.com>
> 
> During region autodiscovery, the region driver always inserts the
> region resource as a child of the root decoder, a CXL WINDOW. It
> has the effect of making a soft reserved resource, with an exactly
> matching address range, a child of the region resource.
> 
> It looks like this in /proc/iomem:
> 
> 2080000000-29dbfffffff : CXL Window 0
>    2080000000-247fffffff : region0
>      2080000000-247fffffff : Soft Reserved
> 
> Search for soft reserved resources that include the region resource,
> and add the new region resource as a child of that found resource.

Don't think the comma is needed here.

> If a soft reserved resource is not found, insert to the root decoder
> as usual.
> 
> With this change, it looks like this:
> 
> 2080000000-29dbfffffff : CXL Window 0
>    2080000000-247fffffff : Soft Reserved
>      2080000000-247fffffff : region0
> 
> This odd parenting only occurs when the resources are an exact match.
> When the region resource only uses part of a soft reserved resource,
> the parenting appears more logical like this:
> 
> 2080000000-29dbfffffff : CXL Window 0
>    2080000000-287fffffff : Soft Reserved
>      2080000000-247fffffff : region0
> 
> Aside from the more logical appearance, this change is in preparation
> for further cleanup in region teardown. A follow-on patch intends to
> find and free soft reserved resources upon region teardown.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> ---
>   drivers/cxl/core/region.c | 32 ++++++++++++++++++++++++++++++--
>   1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index e115ba382e04..36c0c0dd5697 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2709,6 +2709,28 @@ static int match_region_by_range(struct device *dev, void *data)
>   	return rc;
>   }
>   
> +static int insert_resource_soft_reserved(struct resource *soft_res, void *arg)
> +{
> +	struct resource *parent, *new, *res = arg;
> +	bool found = false;
> +
> +	parent = soft_res->parent;
> +	if (!parent)
> +		return 0;
> +
> +	/* Caller provides a copy of soft_res. Find the actual resource. */
> +	for (new = parent->child; new; new = new->sibling) {
> +		if (resource_contains(new, soft_res)) {
> +			found = true;
> +			break;
> +		}
> +	}
> +	if (found)
> +		return insert_resource(new, res) == 0;
> +
> +	return 0;
> +}
> +
>   /* Establish an empty region covering the given HPA range */
>   static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>   					   struct cxl_endpoint_decoder *cxled)
> @@ -2719,7 +2741,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>   	struct cxl_region_params *p;
>   	struct cxl_region *cxlr;
>   	struct resource *res;
> -	int rc;
> +	int rc = 0;
>   
>   	do {
>   		cxlr = __create_region(cxlrd, cxled->mode,
> @@ -2755,7 +2777,13 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>   
>   	*res = DEFINE_RES_MEM_NAMED(hpa->start, range_len(hpa),
>   				    dev_name(&cxlr->dev));
> -	rc = insert_resource(cxlrd->res, res);
> +
> +	/* Try inserting to a Soft Reserved parent, fallback to root decoder */
> +	if (walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED, 0,
> +				res->start, res->end, res,
> +				insert_resource_soft_reserved) != 1)
> +		rc = insert_resource(cxlrd->res, res);
> +
>   	if (rc) {
>   		/*
>   		 * Platform-firmware may not have split resources like "System

Re: [PATCH v2 1/2] cxl/region: Try to add a region resource to a soft reserved parent

[Alison Schofield]

On Wed, Aug 09, 2023 at 04:22:03PM -0700, Dave Jiang wrote:
> 
> 
> On 8/4/23 12:31, alison.schofield@intel.com wrote:
> > From: Alison Schofield <alison.schofield@intel.com>
> > 
> > During region autodiscovery, the region driver always inserts the
> > region resource as a child of the root decoder, a CXL WINDOW. It
> > has the effect of making a soft reserved resource, with an exactly
> > matching address range, a child of the region resource.
> > 
> > It looks like this in /proc/iomem:
> > 
> > 2080000000-29dbfffffff : CXL Window 0
> >    2080000000-247fffffff : region0
> >      2080000000-247fffffff : Soft Reserved
> > 
> > Search for soft reserved resources that include the region resource,
> > and add the new region resource as a child of that found resource.
> 
> Don't think the comma is needed here.

Got it. Thanks!


> 
> > If a soft reserved resource is not found, insert to the root decoder
> > as usual.
> > 
> > With this change, it looks like this:
> > 
> > 2080000000-29dbfffffff : CXL Window 0
> >    2080000000-247fffffff : Soft Reserved
> >      2080000000-247fffffff : region0
> > 
> > This odd parenting only occurs when the resources are an exact match.
> > When the region resource only uses part of a soft reserved resource,
> > the parenting appears more logical like this:
> > 
> > 2080000000-29dbfffffff : CXL Window 0
> >    2080000000-287fffffff : Soft Reserved
> >      2080000000-247fffffff : region0
> > 
> > Aside from the more logical appearance, this change is in preparation
> > for further cleanup in region teardown. A follow-on patch intends to
> > find and free soft reserved resources upon region teardown.
> > 
> > Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> > ---
> >   drivers/cxl/core/region.c | 32 ++++++++++++++++++++++++++++++--
> >   1 file changed, 30 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index e115ba382e04..36c0c0dd5697 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -2709,6 +2709,28 @@ static int match_region_by_range(struct device *dev, void *data)
> >   	return rc;
> >   }
> > +static int insert_resource_soft_reserved(struct resource *soft_res, void *arg)
> > +{
> > +	struct resource *parent, *new, *res = arg;
> > +	bool found = false;
> > +
> > +	parent = soft_res->parent;
> > +	if (!parent)
> > +		return 0;
> > +
> > +	/* Caller provides a copy of soft_res. Find the actual resource. */
> > +	for (new = parent->child; new; new = new->sibling) {
> > +		if (resource_contains(new, soft_res)) {
> > +			found = true;
> > +			break;
> > +		}
> > +	}
> > +	if (found)
> > +		return insert_resource(new, res) == 0;
> > +
> > +	return 0;
> > +}
> > +
> >   /* Establish an empty region covering the given HPA range */
> >   static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> >   					   struct cxl_endpoint_decoder *cxled)
> > @@ -2719,7 +2741,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> >   	struct cxl_region_params *p;
> >   	struct cxl_region *cxlr;
> >   	struct resource *res;
> > -	int rc;
> > +	int rc = 0;
> >   	do {
> >   		cxlr = __create_region(cxlrd, cxled->mode,
> > @@ -2755,7 +2777,13 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> >   	*res = DEFINE_RES_MEM_NAMED(hpa->start, range_len(hpa),
> >   				    dev_name(&cxlr->dev));
> > -	rc = insert_resource(cxlrd->res, res);
> > +
> > +	/* Try inserting to a Soft Reserved parent, fallback to root decoder */
> > +	if (walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED, 0,
> > +				res->start, res->end, res,
> > +				insert_resource_soft_reserved) != 1)
> > +		rc = insert_resource(cxlrd->res, res);
> > +
> >   	if (rc) {
> >   		/*
> >   		 * Platform-firmware may not have split resources like "System

[PATCH v2 2/2] cxl/region: Remove a soft reserved resource at region teardown

[alison.schofield]

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

When CXL regions are created through autodiscovery their resource
may be a child of a soft reserved resource. Today, when such a
region is destroyed, its soft reserved resource remains in place.
That means that the HPA range that the region could release, is
actually unavailable for reuse.

Free the soft reserved resource on region teardown by examining
the alignment of the resources, and handling accordingly. The
two resources, will be exactly aligned, partially aligned, or not
aligned at all.

|----------- "Soft Reserved" -----------|
|-------------- "Region #" -------------|
Exactly aligned. Any dangling children move up to a parent on removal.
The removal of this soft reserved seems guaranteed, however, the
availability of the address range for use depends on complete cleanup
of the region child resources also.

|----------- "Soft Reserved" -----------|
|-------- "Region #" -------|
or
|----------- "Soft Reserved" -----------|
            |-------- "Region #" -------|
Either start or end aligns. Unlike removing a resource, which simply
moves child resources up the resource tree, adjustments fail if any
child resources map the range being truncated. So, this one will fail
for dangling child resources of the region.

|---------- "Soft Reserved" ----------|
        |---- "Region #" ----|
No alignment. Freeing the resource of a region in the middle is possible
if no child resources map the leading or trailing address space.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/core/region.c | 132 +++++++++++++++++++++++++++++++++++---
 1 file changed, 123 insertions(+), 9 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 36c0c0dd5697..b8a02afa3514 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -569,22 +569,136 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
 	return 0;
 }
 
+static int add_soft_reserved(struct resource *parent, resource_size_t start,
+			     resource_size_t len, unsigned long flags)
+{
+	struct resource *res;
+	int rc;
+
+	res = kmalloc(sizeof(*res), GFP_KERNEL);
+	if (!res)
+		return -ENOMEM;
+
+	*res = DEFINE_RES_MEM_NAMED(start, len, "Soft Reserved");
+
+	res->desc = IORES_DESC_SOFT_RESERVED;
+	res->flags = res->flags | flags;
+	rc = insert_resource(parent, res);
+	if (rc)
+		kfree(res);
+
+	return rc;
+}
+
+static void remove_soft_reserved(struct cxl_region *cxlr, struct resource *soft,
+				 resource_size_t start, resource_size_t end)
+{
+	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
+	resource_size_t new_start, new_end;
+	struct resource *parent;
+	unsigned long flags;
+	int rc;
+
+	/* Prevent new usage while removing or adjusting the resource */
+	mutex_lock(&cxlrd->range_lock);
+
+	/* Aligns at both resource start and end */
+	if (soft->start == start && soft->end == end) {
+		rc = remove_resource(soft);
+		if (rc)
+			dev_dbg(&cxlr->dev,
+				"cannot remove soft reserved resource %pr\n",
+				soft);
+		else
+			kfree(soft);
+
+		goto out;
+	}
+
+	/* Aligns at either resource start or end */
+	if (soft->start == start || soft->end == end) {
+		if (soft->start == start) {
+			new_start = end + 1;
+			new_end = soft->end;
+		} else {
+			new_start = soft->start;
+			new_end = start + 1;
+		}
+		rc =  adjust_resource(soft, new_start, new_end - new_start + 1);
+		if (rc)
+			dev_dbg(&cxlr->dev,
+				"cannot adjust soft reserved resource %pr\n",
+				soft);
+		goto out;
+	}
+
+	/*
+	 * No alignment. Attempt a 3-way split that removes the part of
+	 * the resource the region occupied, and then creates new soft
+	 * reserved resources for the leading and trailing addr space.
+	 * adjust_resource() will stop the attempt if there are any
+	 * child resources.
+	 */
+
+	/* Save the original soft reserved resource params before adjusting */
+	new_start = soft->start;
+	new_end = soft->end;
+	parent = soft->parent;
+	flags = soft->flags;
+
+	rc = adjust_resource(soft, start, end - start);
+	if (rc) {
+		dev_dbg(&cxlr->dev,
+			"cannot adjust soft reserved resource %pr\n", soft);
+		goto out;
+	}
+	rc = remove_resource(soft);
+	if (rc)
+		dev_warn(&cxlr->dev,
+			 "cannot remove soft reserved resource %pr\n", soft);
+
+	rc = add_soft_reserved(parent, new_start, start - new_start, flags);
+	if (rc)
+		dev_warn(&cxlr->dev,
+			 "cannot add new soft reserved resource at %pa\n",
+			 &new_start);
+
+	rc = add_soft_reserved(parent, end + 1, new_end - end, flags);
+	if (rc)
+		dev_warn(&cxlr->dev,
+			 "cannot add new soft reserved resource at %pa + 1\n",
+			 &end);
+out:
+	mutex_unlock(&cxlrd->range_lock);
+}
+
 static void cxl_region_iomem_release(struct cxl_region *cxlr)
 {
 	struct cxl_region_params *p = &cxlr->params;
+	struct resource *parent, *res = p->res;
+	resource_size_t start, end;
 
 	if (device_is_registered(&cxlr->dev))
 		lockdep_assert_held_write(&cxl_region_rwsem);
-	if (p->res) {
-		/*
-		 * Autodiscovered regions may not have been able to insert their
-		 * resource.
-		 */
-		if (p->res->parent)
-			remove_resource(p->res);
-		kfree(p->res);
-		p->res = NULL;
+	if (!res)
+		return;
+	/*
+	 * Autodiscovered regions may not have been able to insert their
+	 * resource. If a Soft Reserved parent resource exists, try to
+	 * remove that also.
+	 */
+	if (p->res->parent) {
+		parent = p->res->parent;
+		start = p->res->start;
+		end = p->res->end;
+		remove_resource(p->res);
+		if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags) &&
+		    parent->desc == IORES_DESC_SOFT_RESERVED)
+			remove_soft_reserved(cxlr, parent, start, end);
 	}
+
+	kfree(p->res);
+	p->res = NULL;
 }
 
 static int free_hpa(struct cxl_region *cxlr)
-- 
2.37.3

Re: [PATCH v2 2/2] cxl/region: Remove a soft reserved resource at region teardown

[Dave Jiang]

On 8/4/23 12:31, alison.schofield@intel.com wrote:
> From: Alison Schofield <alison.schofield@intel.com>
> 
> When CXL regions are created through autodiscovery their resource
> may be a child of a soft reserved resource. Today, when such a
> region is destroyed, its soft reserved resource remains in place.
> That means that the HPA range that the region could release, is
> actually unavailable for reuse.

I think it reads better without the comma here.

> 
> Free the soft reserved resource on region teardown by examining
> the alignment of the resources, and handling accordingly. The
> two resources, will be exactly aligned, partially aligned, or not
> aligned at all.
> 
> |----------- "Soft Reserved" -----------|
> |-------------- "Region #" -------------|
> Exactly aligned. Any dangling children move up to a parent on removal.
> The removal of this soft reserved seems guaranteed, however, the
> availability of the address range for use depends on complete cleanup
> of the region child resources also.
> 
> |----------- "Soft Reserved" -----------|
> |-------- "Region #" -------|
> or
> |----------- "Soft Reserved" -----------|
>              |-------- "Region #" -------|
> Either start or end aligns. Unlike removing a resource, which simply
> moves child resources up the resource tree, adjustments fail if any
> child resources map the range being truncated. So, this one will fail
> for dangling child resources of the region.
> 
> |---------- "Soft Reserved" ----------|
>          |---- "Region #" ----|
> No alignment. Freeing the resource of a region in the middle is possible
> if no child resources map the leading or trailing address space.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> ---
>   drivers/cxl/core/region.c | 132 +++++++++++++++++++++++++++++++++++---
>   1 file changed, 123 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 36c0c0dd5697..b8a02afa3514 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -569,22 +569,136 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
>   	return 0;
>   }
>   
> +static int add_soft_reserved(struct resource *parent, resource_size_t start,
> +			     resource_size_t len, unsigned long flags)
> +{
> +	struct resource *res;
> +	int rc;
> +
> +	res = kmalloc(sizeof(*res), GFP_KERNEL);
> +	if (!res)
> +		return -ENOMEM;
> +
> +	*res = DEFINE_RES_MEM_NAMED(start, len, "Soft Reserved");
> +
> +	res->desc = IORES_DESC_SOFT_RESERVED;
> +	res->flags = res->flags | flags;
> +	rc = insert_resource(parent, res);
> +	if (rc)
> +		kfree(res);
> +
> +	return rc;
> +}
> +
> +static void remove_soft_reserved(struct cxl_region *cxlr, struct resource *soft,
> +				 resource_size_t start, resource_size_t end)
> +{
> +	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
> +	resource_size_t new_start, new_end;
> +	struct resource *parent;
> +	unsigned long flags;
> +	int rc;
> +
> +	/* Prevent new usage while removing or adjusting the resource */
> +	mutex_lock(&cxlrd->range_lock);
> +
> +	/* Aligns at both resource start and end */
> +	if (soft->start == start && soft->end == end) {
> +		rc = remove_resource(soft);
> +		if (rc)
> +			dev_dbg(&cxlr->dev,
> +				"cannot remove soft reserved resource %pr\n",
> +				soft);
> +		else
> +			kfree(soft);
> +
> +		goto out;
> +	}
> +
> +	/* Aligns at either resource start or end */
> +	if (soft->start == start || soft->end == end) {
> +		if (soft->start == start) {
> +			new_start = end + 1;
> +			new_end = soft->end;
> +		} else {
> +			new_start = soft->start;
> +			new_end = start + 1;
> +		}
> +		rc =  adjust_resource(soft, new_start, new_end - new_start + 1);
> +		if (rc)
> +			dev_dbg(&cxlr->dev,
> +				"cannot adjust soft reserved resource %pr\n",
> +				soft);
> +		goto out;
> +	}
> +
> +	/*
> +	 * No alignment. Attempt a 3-way split that removes the part of
> +	 * the resource the region occupied, and then creates new soft
> +	 * reserved resources for the leading and trailing addr space.
> +	 * adjust_resource() will stop the attempt if there are any
> +	 * child resources.
> +	 */
> +
> +	/* Save the original soft reserved resource params before adjusting */
> +	new_start = soft->start;
> +	new_end = soft->end;
> +	parent = soft->parent;
> +	flags = soft->flags;
> +
> +	rc = adjust_resource(soft, start, end - start);
> +	if (rc) {
> +		dev_dbg(&cxlr->dev,
> +			"cannot adjust soft reserved resource %pr\n", soft);
> +		goto out;
> +	}
> +	rc = remove_resource(soft);
> +	if (rc)
> +		dev_warn(&cxlr->dev,
> +			 "cannot remove soft reserved resource %pr\n", soft);
> +
> +	rc = add_soft_reserved(parent, new_start, start - new_start, flags);
> +	if (rc)
> +		dev_warn(&cxlr->dev,
> +			 "cannot add new soft reserved resource at %pa\n",
> +			 &new_start);
> +
> +	rc = add_soft_reserved(parent, end + 1, new_end - end, flags);
> +	if (rc)
> +		dev_warn(&cxlr->dev,
> +			 "cannot add new soft reserved resource at %pa + 1\n",
> +			 &end);
> +out:
> +	mutex_unlock(&cxlrd->range_lock);
> +}
> +
>   static void cxl_region_iomem_release(struct cxl_region *cxlr)
>   {
>   	struct cxl_region_params *p = &cxlr->params;
> +	struct resource *parent, *res = p->res;
> +	resource_size_t start, end;
>   
>   	if (device_is_registered(&cxlr->dev))
>   		lockdep_assert_held_write(&cxl_region_rwsem);
> -	if (p->res) {
> -		/*
> -		 * Autodiscovered regions may not have been able to insert their
> -		 * resource.
> -		 */
> -		if (p->res->parent)
> -			remove_resource(p->res);
> -		kfree(p->res);
> -		p->res = NULL;
> +	if (!res)
> +		return;
> +	/*
> +	 * Autodiscovered regions may not have been able to insert their
> +	 * resource. If a Soft Reserved parent resource exists, try to
> +	 * remove that also.
> +	 */
> +	if (p->res->parent) {
> +		parent = p->res->parent;
> +		start = p->res->start;
> +		end = p->res->end;
> +		remove_resource(p->res);
> +		if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags) &&
> +		    parent->desc == IORES_DESC_SOFT_RESERVED)
> +			remove_soft_reserved(cxlr, parent, start, end);
>   	}
> +
> +	kfree(p->res);
> +	p->res = NULL;
>   }
>   
>   static int free_hpa(struct cxl_region *cxlr)

Re: [PATCH v2 2/2] cxl/region: Remove a soft reserved resource at region teardown

[Alison Schofield]

On Wed, Aug 09, 2023 at 04:34:43PM -0700, Dave Jiang wrote:
> 
> 
> On 8/4/23 12:31, alison.schofield@intel.com wrote:
> > From: Alison Schofield <alison.schofield@intel.com>
> > 
> > When CXL regions are created through autodiscovery their resource
> > may be a child of a soft reserved resource. Today, when such a
> > region is destroyed, its soft reserved resource remains in place.
> > That means that the HPA range that the region could release, is
> > actually unavailable for reuse.
> 
> I think it reads better without the comma here.

Agree. Thanks!
Alison

> 
> > 
> > Free the soft reserved resource on region teardown by examining
> > the alignment of the resources, and handling accordingly. The
> > two resources, will be exactly aligned, partially aligned, or not
> > aligned at all.
> > 
> > |----------- "Soft Reserved" -----------|
> > |-------------- "Region #" -------------|
> > Exactly aligned. Any dangling children move up to a parent on removal.
> > The removal of this soft reserved seems guaranteed, however, the
> > availability of the address range for use depends on complete cleanup
> > of the region child resources also.
> > 
> > |----------- "Soft Reserved" -----------|
> > |-------- "Region #" -------|
> > or
> > |----------- "Soft Reserved" -----------|
> >              |-------- "Region #" -------|
> > Either start or end aligns. Unlike removing a resource, which simply
> > moves child resources up the resource tree, adjustments fail if any
> > child resources map the range being truncated. So, this one will fail
> > for dangling child resources of the region.
> > 
> > |---------- "Soft Reserved" ----------|
> >          |---- "Region #" ----|
> > No alignment. Freeing the resource of a region in the middle is possible
> > if no child resources map the leading or trailing address space.
> > 
> > Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> > ---
> >   drivers/cxl/core/region.c | 132 +++++++++++++++++++++++++++++++++++---
> >   1 file changed, 123 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index 36c0c0dd5697..b8a02afa3514 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -569,22 +569,136 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
> >   	return 0;
> >   }
> > +static int add_soft_reserved(struct resource *parent, resource_size_t start,
> > +			     resource_size_t len, unsigned long flags)
> > +{
> > +	struct resource *res;
> > +	int rc;
> > +
> > +	res = kmalloc(sizeof(*res), GFP_KERNEL);
> > +	if (!res)
> > +		return -ENOMEM;
> > +
> > +	*res = DEFINE_RES_MEM_NAMED(start, len, "Soft Reserved");
> > +
> > +	res->desc = IORES_DESC_SOFT_RESERVED;
> > +	res->flags = res->flags | flags;
> > +	rc = insert_resource(parent, res);
> > +	if (rc)
> > +		kfree(res);
> > +
> > +	return rc;
> > +}
> > +
> > +static void remove_soft_reserved(struct cxl_region *cxlr, struct resource *soft,
> > +				 resource_size_t start, resource_size_t end)
> > +{
> > +	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
> > +	resource_size_t new_start, new_end;
> > +	struct resource *parent;
> > +	unsigned long flags;
> > +	int rc;
> > +
> > +	/* Prevent new usage while removing or adjusting the resource */
> > +	mutex_lock(&cxlrd->range_lock);
> > +
> > +	/* Aligns at both resource start and end */
> > +	if (soft->start == start && soft->end == end) {
> > +		rc = remove_resource(soft);
> > +		if (rc)
> > +			dev_dbg(&cxlr->dev,
> > +				"cannot remove soft reserved resource %pr\n",
> > +				soft);
> > +		else
> > +			kfree(soft);
> > +
> > +		goto out;
> > +	}
> > +
> > +	/* Aligns at either resource start or end */
> > +	if (soft->start == start || soft->end == end) {
> > +		if (soft->start == start) {
> > +			new_start = end + 1;
> > +			new_end = soft->end;
> > +		} else {
> > +			new_start = soft->start;
> > +			new_end = start + 1;
> > +		}
> > +		rc =  adjust_resource(soft, new_start, new_end - new_start + 1);
> > +		if (rc)
> > +			dev_dbg(&cxlr->dev,
> > +				"cannot adjust soft reserved resource %pr\n",
> > +				soft);
> > +		goto out;
> > +	}
> > +
> > +	/*
> > +	 * No alignment. Attempt a 3-way split that removes the part of
> > +	 * the resource the region occupied, and then creates new soft
> > +	 * reserved resources for the leading and trailing addr space.
> > +	 * adjust_resource() will stop the attempt if there are any
> > +	 * child resources.
> > +	 */
> > +
> > +	/* Save the original soft reserved resource params before adjusting */
> > +	new_start = soft->start;
> > +	new_end = soft->end;
> > +	parent = soft->parent;
> > +	flags = soft->flags;
> > +
> > +	rc = adjust_resource(soft, start, end - start);
> > +	if (rc) {
> > +		dev_dbg(&cxlr->dev,
> > +			"cannot adjust soft reserved resource %pr\n", soft);
> > +		goto out;
> > +	}
> > +	rc = remove_resource(soft);
> > +	if (rc)
> > +		dev_warn(&cxlr->dev,
> > +			 "cannot remove soft reserved resource %pr\n", soft);
> > +
> > +	rc = add_soft_reserved(parent, new_start, start - new_start, flags);
> > +	if (rc)
> > +		dev_warn(&cxlr->dev,
> > +			 "cannot add new soft reserved resource at %pa\n",
> > +			 &new_start);
> > +
> > +	rc = add_soft_reserved(parent, end + 1, new_end - end, flags);
> > +	if (rc)
> > +		dev_warn(&cxlr->dev,
> > +			 "cannot add new soft reserved resource at %pa + 1\n",
> > +			 &end);
> > +out:
> > +	mutex_unlock(&cxlrd->range_lock);
> > +}
> > +
> >   static void cxl_region_iomem_release(struct cxl_region *cxlr)
> >   {
> >   	struct cxl_region_params *p = &cxlr->params;
> > +	struct resource *parent, *res = p->res;
> > +	resource_size_t start, end;
> >   	if (device_is_registered(&cxlr->dev))
> >   		lockdep_assert_held_write(&cxl_region_rwsem);
> > -	if (p->res) {
> > -		/*
> > -		 * Autodiscovered regions may not have been able to insert their
> > -		 * resource.
> > -		 */
> > -		if (p->res->parent)
> > -			remove_resource(p->res);
> > -		kfree(p->res);
> > -		p->res = NULL;
> > +	if (!res)
> > +		return;
> > +	/*
> > +	 * Autodiscovered regions may not have been able to insert their
> > +	 * resource. If a Soft Reserved parent resource exists, try to
> > +	 * remove that also.
> > +	 */
> > +	if (p->res->parent) {
> > +		parent = p->res->parent;
> > +		start = p->res->start;
> > +		end = p->res->end;
> > +		remove_resource(p->res);
> > +		if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags) &&
> > +		    parent->desc == IORES_DESC_SOFT_RESERVED)
> > +			remove_soft_reserved(cxlr, parent, start, end);
> >   	}
> > +
> > +	kfree(p->res);
> > +	p->res = NULL;
> >   }
> >   static int free_hpa(struct cxl_region *cxlr)