cxl/region: Match auto-discovered region decoders by HPA range
[email protected]
maintainerPATCH v2 1/1 cxl/region: Match auto-discovered region decoders by HPA range
From: Alison Schofield <[email protected]>
Currently, when the region driver attaches a region to a port, it selects the ports next available decoder to program.
With the addition of auto-discovered regions, a port decoder has already been programmed so grabbing the next available decoder can be a mismatch when there is more than one region using the port.
The failure appears like this with CXL DEBUG enabled:
[] cxl_core:alloc_region_ref:754: cxl region0: endpoint9: HPA order violation region0:[mem 0x14780000000-0x1478fffffff flags 0x200] vs [mem 0x880000000-0x185fffffff flags 0x200] [] cxl_core:cxl_port_attach_region:972: cxl region0: endpoint9: failed to allocate region reference
When CXL DEBUG is not enabled, there is no failure message. The region just never materializes. Users can suspect this issue if they know their firmware has programmed decoders so that more than one region is using a port. Note that the problem may appear intermittently, ie not on every reboot.
Add a matching method for auto-discovered regions that finds a decoder based on an HPA range. The decoder range must exactly match the region resource parameter.
---
Changes in v2:
- Use cxlr->params for HPA match rather than requiring cxled (Dan)
- dev_warn() if decoder already assigned to a region (Dan)
- Add failure footprint to commit log (Dan)
- Add Fixes Tag (Dan)
- v1: https://lore.kernel.org/linux-cxl/[email protected]/
drivers/cxl/core/region.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-)
drivers/cxl/core/region.c +28 -1
@@ -717,13 +717,40 @@ static int match_free_decoder(struct device *dev, void *data)return 0 ; } +static int match_auto_decoder (struct device *dev,void *data) +{ +struct cxl_region_params *p = data; +struct cxl_decoder *cxld; +struct range *r; + +if (!is_switch_decoder (dev)) +return 0 ; + + cxld =to_cxl_decoder (dev); + r = &cxld->hpa_range; + +if (p->res && p->res->start == r->start && p->res->end == r->end) { +if (cxld->region) { +dev_WARN (dev,"decoder already attached to %s\n" , +dev_name (&cxld->region->dev)); +return 0 ; + } +return 1 ; + } +return 0 ; +} +static struct cxl_decoder *cxl_region_find_decoder (struct cxl_port *port,struct cxl_region *cxlr) {struct device *dev;int id =0 ; - dev =device_find_child (&port->dev, &id, match_free_decoder); +if (test_bit (CXL_REGION_F_AUTO , &cxlr->flags)) + dev =device_find_child (&port->dev, &cxlr->params, + match_auto_decoder); +else + dev =device_find_child (&port->dev, &id, match_free_decoder);if (!dev)return NULL ;/*
base-commit: fe77cc2e5a6a7c85f5c6ef8a39d7694ffc7f41c9
Signature · 1 line
2.37.3
Quoted 20 lines · On 8/21/23 18:43, [email protected] wrote:
From: Alison Schofield <[email protected]>
Currently, when the region driver attaches a region to a port, it selects the ports next available decoder to program.
With the addition of auto-discovered regions, a port decoder has already been programmed so grabbing the next available decoder can be a mismatch when there is more than one region using the port.
The failure appears like this with CXL DEBUG enabled:
[] cxl_core:alloc_region_ref:754: cxl region0: endpoint9: HPA order violation region0:[mem 0x14780000000-0x1478fffffff flags
0x200] vs [mem 0x880000000-0x185fffffff flags0x200] [] cxl_core:cxl_port_attach_region:972: cxl region0: endpoint9: failed to allocate region referenceWhen CXL DEBUG is not enabled, there is no failure message. The region just never materializes. Users can suspect this issue if they know their firmware has programmed decoders so that more than one region is using a port. Note that the problem may appear intermittently, ie not on every reboot.
Quoted 6 lines
Add a matching method for auto-discovered regions that finds a decoder based on an HPA range. The decoder range must exactly match the region resource parameter.
Fixes a32320b71f08 ("cxl/region: Add region autodiscovery")Signed-off-by Alison Schofield <[email protected]>
Quoted 60 lines
---
Changes in v2:
- Usecxlr->paramsfor HPA match rather than requiring cxled (Dan)
-dev_warn()if decoder already assigned to a region (Dan)
- Add failure footprint to commit log (Dan)
- Add Fixes Tag (Dan)
- v1: https://lore.kernel.org/linux-cxl/[email protected]/drivers/cxl/core/region.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-)drivers/cxl/core/region.c +28
-1@@ -717,13 +717,40 @@ static int match_free_decoder(struct device *dev, void *data)return 0 ; } +static int match_auto_decoder (struct device *dev,void *data) +{ +struct cxl_region_params *p = data; +struct cxl_decoder *cxld; +struct range *r; + +if (!is_switch_decoder (dev)) +return 0 ; + + cxld =to_cxl_decoder (dev); + r = &cxld->hpa_range; + +if (p->res && p->res->start == r->start && p->res->end == r->end) { +if (cxld->region) { +dev_WARN (dev,"decoder already attached to %s\n" , +dev_name (&cxld->region->dev)); +return 0 ; + } +return 1 ; + } +return 0 ; +} +static struct cxl_decoder *cxl_region_find_decoder (struct cxl_port *port,struct cxl_region *cxlr) {struct device *dev;int id =0 ; - dev =device_find_child (&port->dev, &id, match_free_decoder); +if (test_bit (CXL_REGION_F_AUTO , &cxlr->flags)) + dev =device_find_child (&port->dev, &cxlr->params, + match_auto_decoder); +else + dev =device_find_child (&port->dev, &id, match_free_decoder);if (!dev)return NULL ;/* base-commit:
fe77cc2e5a6a7c85f5c6ef8a39d7694ffc7f41c9
Quoted 20 lines · On Mon, 21 Aug 2023, [email protected] wrote:
From: Alison Schofield <[email protected]>
Currently, when the region driver attaches a region to a port, it selects the ports next available decoder to program.
With the addition of auto-discovered regions, a port decoder has already been programmed so grabbing the next available decoder can be a mismatch when there is more than one region using the port.
The failure appears like this with CXL DEBUG enabled:
[] cxl_core:alloc_region_ref:754: cxl region0: endpoint9: HPA order violation region0:[mem 0x14780000000-0x1478fffffff flags
0x200] vs [mem 0x880000000-0x185fffffff flags0x200] [] cxl_core:cxl_port_attach_region:972: cxl region0: endpoint9: failed to allocate region referenceWhen CXL DEBUG is not enabled, there is no failure message. The region just never materializes. Users can suspect this issue if they know their firmware has programmed decoders so that more than one region is using a port. Note that the problem may appear intermittently, ie not on every reboot.
Quoted 6 lines
Add a matching method for auto-discovered regions that finds a decoder based on an HPA range. The decoder range must exactly match the region resource parameter.
Fixes a32320b71f08 ("cxl/region: Add region autodiscovery")Signed-off-by Alison Schofield <[email protected]>
Quoted 20 lines · On Mon, 21 Aug 2023 18:43:03 -0700 [email protected] wrote:
From: Alison Schofield <[email protected]>
Currently, when the region driver attaches a region to a port, it selects the ports next available decoder to program.
With the addition of auto-discovered regions, a port decoder has already been programmed so grabbing the next available decoder can be a mismatch when there is more than one region using the port.
The failure appears like this with CXL DEBUG enabled:
[] cxl_core:alloc_region_ref:754: cxl region0: endpoint9: HPA order violation region0:[mem 0x14780000000-0x1478fffffff flags
0x200] vs [mem 0x880000000-0x185fffffff flags0x200] [] cxl_core:cxl_port_attach_region:972: cxl region0: endpoint9: failed to allocate region referenceWhen CXL DEBUG is not enabled, there is no failure message. The region just never materializes. Users can suspect this issue if they know their firmware has programmed decoders so that more than one region is using a port. Note that the problem may appear intermittently, ie not on every reboot.
Quoted 6 lines
Add a matching method for auto-discovered regions that finds a decoder based on an HPA range. The decoder range must exactly match the region resource parameter.
Fixes a32320b71f08 ("cxl/region: Add region autodiscovery")Signed-off-by Alison Schofield <[email protected]>
Bikeshed time...
Quoted 17 lines
---
Changes in v2:
- Usecxlr->paramsfor HPA match rather than requiring cxled (Dan)
-dev_warn()if decoder already assigned to a region (Dan)
- Add failure footprint to commit log (Dan)
- Add Fixes Tag (Dan)
- v1: https://lore.kernel.org/linux-cxl/[email protected]/drivers/cxl/core/region.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-)drivers/cxl/core/region.c +0
-0
drivers/cxl/core/region.c static int match_free_decoder(struct device *dev, void *data) · line 720
Quoted 4 lines
drivers/cxl/core/region.c +1
-0@@ -717,13 +717,40 @@ static int match_free_decoder(struct device *dev, void *data)return 0 ; } +static int match_auto_decoder (struct device *dev,void *data)
Does more than matching a decoder and in the warning path doesn't actually match it (not returning 1 so we carry on).
So perhaps a rename?
Quoted 6 lines
drivers/cxl/core/region.c +6
-0+{ +struct cxl_region_params *p = data; +struct cxl_decoder *cxld; +struct range *r; + +if (!is_switch_decoder (dev))
drivers/cxl/core/region.c static int match_free_decoder(struct device *dev, void *data) · line 736
Quoted 10 lines
drivers/cxl/core/region.c +10
-0+return 0 ; + + cxld =to_cxl_decoder (dev); + r = &cxld->hpa_range; + +if (p->res && p->res->start == r->start && p->res->end == r->end) { +if (cxld->region) { +dev_WARN (dev,"decoder already attached to %s\n" , +dev_name (&cxld->region->dev)); +return 0 ;
Not obvious to me why we carry on looking for matching regions if we have found a precise match (even if it's already attached).
I'd expect return 1 here. Maybe a comment on why it makes sense to keep trying?
Quoted 23 lines
drivers/cxl/core/region.c +11
-1+ } +return 1 ; + } +return 0 ; +} +static struct cxl_decoder *cxl_region_find_decoder (struct cxl_port *port,struct cxl_region *cxlr) {struct device *dev;int id =0 ; - dev =device_find_child (&port->dev, &id, match_free_decoder); +if (test_bit (CXL_REGION_F_AUTO , &cxlr->flags)) + dev =device_find_child (&port->dev, &cxlr->params, + match_auto_decoder); +else + dev =device_find_child (&port->dev, &id, match_free_decoder);if (!dev)return NULL ;/* base-commit:
fe77cc2e5a6a7c85f5c6ef8a39d7694ffc7f41c9
Alison Schofield
maintainerQuoted 23 lines · Jonathan Cameron
Quoted 20 lines · On Mon, 21 Aug 2023 18:43:03 -0700 [email protected] wrote:
From: Alison Schofield <[email protected]>
Currently, when the region driver attaches a region to a port, it selects the ports next available decoder to program.
With the addition of auto-discovered regions, a port decoder has already been programmed so grabbing the next available decoder can be a mismatch when there is more than one region using the port.
The failure appears like this with CXL DEBUG enabled:
[] cxl_core:alloc_region_ref:754: cxl region0: endpoint9: HPA order violation region0:[mem 0x14780000000-0x1478fffffff flags
0x200] vs [mem 0x880000000-0x185fffffff flags0x200] [] cxl_core:cxl_port_attach_region:972: cxl region0: endpoint9: failed to allocate region referenceWhen CXL DEBUG is not enabled, there is no failure message. The region just never materializes. Users can suspect this issue if they know their firmware has programmed decoders so that more than one region is using a port. Note that the problem may appear intermittently, ie not on every reboot.
Quoted 7 lines
Quoted 6 lines
Add a matching method for auto-discovered regions that finds a decoder based on an HPA range. The decoder range must exactly match the region resource parameter.
Fixes a32320b71f08 ("cxl/region: Add region autodiscovery")Signed-off-by Alison Schofield <[email protected]>Bikeshed time...
Not bikeshed, good catch -
Quoted 21 lines
Quoted 21 lines
---
Changes in v2:
- Usecxlr->paramsfor HPA match rather than requiring cxled (Dan)
-dev_warn()if decoder already assigned to a region (Dan)
- Add failure footprint to commit log (Dan)
- Add Fixes Tag (Dan)
- v1: https://lore.kernel.org/linux-cxl/[email protected]/drivers/cxl/core/region.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-)drivers/cxl/core/region.c +0
-0@@ -717,13 +717,40 @@ static int match_free_decoder(struct device *dev, void *data)return 0 ; }
Quoted 6 lines
drivers/cxl/core/region.c static int match_free_decoder(struct device *dev, void *data) · line 720
Quoted 1 line
drivers/cxl/core/region.c +1
-0+static int match_auto_decoder (struct device *dev,void *data)Does more than matching a decoder and in the warning path doesn't actually match it (not returning 1 so we carry on).
So perhaps a rename?
I've updated to just do the match. Checking for an attached region was redundant as it's already done in the call path.
Thanks for the review!
Quoted 46 lines
Quoted 7 lines
drivers/cxl/core/region.c +6
-0+{ +struct cxl_region_params *p = data; +struct cxl_decoder *cxld; +struct range *r; + +if (!is_switch_decoder (dev))drivers/cxl/core/region.c static int match_free_decoder(struct device *dev, void *data) · line 736
Quoted 10 lines
drivers/cxl/core/region.c +10
-0+return 0 ; + + cxld =to_cxl_decoder (dev); + r = &cxld->hpa_range; + +if (p->res && p->res->start == r->start && p->res->end == r->end) { +if (cxld->region) { +dev_WARN (dev,"decoder already attached to %s\n" , +dev_name (&cxld->region->dev)); +return 0 ;Not obvious to me why we carry on looking for matching regions if we have found a precise match (even if it's already attached).
I'd expect return 1 here. Maybe a comment on why it makes sense to keep trying?Quoted 23 lines
drivers/cxl/core/region.c +11
-1+ } +return 1 ; + } +return 0 ; +} +static struct cxl_decoder *cxl_region_find_decoder (struct cxl_port *port,struct cxl_region *cxlr) {struct device *dev;int id =0 ; - dev =device_find_child (&port->dev, &id, match_free_decoder); +if (test_bit (CXL_REGION_F_AUTO , &cxlr->flags)) + dev =device_find_child (&port->dev, &cxlr->params, + match_auto_decoder); +else + dev =device_find_child (&port->dev, &id, match_free_decoder);if (!dev)return NULL ;/* base-commit:
fe77cc2e5a6a7c85f5c6ef8a39d7694ffc7f41c9