Re: [PATCH 2/5] cxl/region: Add dynamic capacity cxl region support.

[Dave Jiang <dave.jiang@intel.com>]

On 6/15/23 11:12, Ira Weiny wrote:
> Dave Jiang wrote:
>>
>>
>> On 6/14/23 12:16, ira.weiny@intel.com wrote:
>>> From: Navneet Singh <navneet.singh@intel.com>
>>>
>>> CXL devices optionally support dynamic capacity. CXL Regions must be
>>> created to access this capacity.
>>>
>>> Add sysfs entries to create dynamic capacity cxl regions. Provide a new
>>> Dynamic Capacity decoder mode which targets dynamic capacity on devices
>>> which are added to that region.
>>>
>>> Below are the steps to create and delete dynamic capacity region0
>>> (example).
>>>
>>>       region=$(cat /sys/bus/cxl/devices/decoder0.0/create_dc_region)
>>>       echo $region> /sys/bus/cxl/devices/decoder0.0/create_dc_region
>>>       echo 256 > /sys/bus/cxl/devices/$region/interleave_granularity
>>>       echo 1 > /sys/bus/cxl/devices/$region/interleave_ways
>>>
>>>       echo "dc0" >/sys/bus/cxl/devices/decoder1.0/mode
>>>       echo 0x400000000 >/sys/bus/cxl/devices/decoder1.0/dpa_size
>>>
>>>       echo 0x400000000 > /sys/bus/cxl/devices/$region/size
>>>       echo  "decoder1.0" > /sys/bus/cxl/devices/$region/target0
>>>       echo 1 > /sys/bus/cxl/devices/$region/commit
>>>       echo $region > /sys/bus/cxl/drivers/cxl_region/bind
>>>
>>>       echo $region> /sys/bus/cxl/devices/decoder0.0/delete_region
>>>
>>> Signed-off-by: Navneet Singh <navneet.singh@intel.com>
>>>
>>> ---
>>> [iweiny: fixups]
>>> [iweiny: remove unused CXL_DC_REGION_MODE macro]
>>> [iweiny: Make dc_mode_to_region_index static]
>>> [iweiny: simplify <sysfs>/create_dc_region]
>>> [iweiny: introduce decoder_mode_is_dc]
>>> [djbw: fixups, no sign-off: preview only]
>>> ---
>>>    drivers/cxl/Kconfig       |  11 +++
>>>    drivers/cxl/core/core.h   |   7 ++
>>>    drivers/cxl/core/hdm.c    | 234 ++++++++++++++++++++++++++++++++++++++++++----
>>>    drivers/cxl/core/port.c   |  18 ++++
>>>    drivers/cxl/core/region.c | 135 ++++++++++++++++++++++++--
>>>    drivers/cxl/cxl.h         |  28 ++++++
>>>    drivers/dax/cxl.c         |   4 +
>>>    7 files changed, 409 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
>>> index ff4e78117b31..df034889d053 100644
>>> --- a/drivers/cxl/Kconfig
>>> +++ b/drivers/cxl/Kconfig
>>> @@ -121,6 +121,17 @@ config CXL_REGION
>>>    
>>>    	  If unsure say 'y'
>>>    
>>> +config CXL_DCD
>>> +	bool "CXL: DCD Support"
>>> +	default CXL_BUS
>>> +	depends on CXL_REGION
>>> +	help
>>> +	  Enable the CXL core to provision CXL DCD regions.
>>> +	  CXL devices optionally support dynamic capacity and DCD region
>>> +	  maps the dynamic capacity regions DPA's into Host HPA ranges.
>>> +
>>> +	  If unsure say 'y'
>>> +
>>>    config CXL_REGION_INVALIDATION_TEST
>>>    	bool "CXL: Region Cache Management Bypass (TEST)"
>>>    	depends on CXL_REGION
>>> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
>>> index 27f0968449de..725700ab5973 100644
>>> --- a/drivers/cxl/core/core.h
>>> +++ b/drivers/cxl/core/core.h
>>> @@ -9,6 +9,13 @@ extern const struct device_type cxl_nvdimm_type;
>>>    
>>>    extern struct attribute_group cxl_base_attribute_group;
>>>    
>>> +#ifdef CONFIG_CXL_DCD
>>> +extern struct device_attribute dev_attr_create_dc_region;
>>> +#define SET_CXL_DC_REGION_ATTR(x) (&dev_attr_##x.attr),
>>> +#else
>>> +#define SET_CXL_DC_REGION_ATTR(x)
>>> +#endif
>>> +
>>>    #ifdef CONFIG_CXL_REGION
>>>    extern struct device_attribute dev_attr_create_pmem_region;
>>>    extern struct device_attribute dev_attr_create_ram_region;
>>> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
>>> index 514d30131d92..29649b47d177 100644
>>> --- a/drivers/cxl/core/hdm.c
>>> +++ b/drivers/cxl/core/hdm.c
>>> @@ -233,14 +233,23 @@ static void __cxl_dpa_release(struct cxl_endpoint_decoder *cxled)
>>>    	struct cxl_dev_state *cxlds = cxlmd->cxlds;
>>>    	struct resource *res = cxled->dpa_res;
>>>    	resource_size_t skip_start;
>>> +	resource_size_t skipped = cxled->skip;
>>>    
>>>    	lockdep_assert_held_write(&cxl_dpa_rwsem);
>>>    
>>>    	/* save @skip_start, before @res is released */
>>> -	skip_start = res->start - cxled->skip;
>>> +	skip_start = res->start - skipped;
>>>    	__release_region(&cxlds->dpa_res, res->start, resource_size(res));
>>> -	if (cxled->skip)
>>> -		__release_region(&cxlds->dpa_res, skip_start, cxled->skip);
>>> +	if (cxled->skip != 0) {
>>> +		while (skipped != 0) {
>>> +			res = xa_load(&cxled->skip_res, skip_start);
>>> +			__release_region(&cxlds->dpa_res, skip_start,
>>> +							resource_size(res));
>>> +			xa_erase(&cxled->skip_res, skip_start);
>>> +			skip_start += resource_size(res);
>>> +			skipped -= resource_size(res);
>>> +			}
>>> +	}
>>>    	cxled->skip = 0;
>>>    	cxled->dpa_res = NULL;
>>>    	put_device(&cxled->cxld.dev);
>>> @@ -267,6 +276,19 @@ static void devm_cxl_dpa_release(struct cxl_endpoint_decoder *cxled)
>>>    	__cxl_dpa_release(cxled);
>>>    }
>>>    
>>> +static int dc_mode_to_region_index(enum cxl_decoder_mode mode)
>>> +{
>>> +	int index = 0;
>>> +
>>> +	for (int i = CXL_DECODER_DC0; i <= CXL_DECODER_DC7; i++) {
>>> +		if (mode == i)
>>> +			return index;
>>> +		index++;
>>> +	}
>>> +
>>> +	return -EINVAL;
>>> +}
>>> +
>>>    static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>>>    			     resource_size_t base, resource_size_t len,
>>>    			     resource_size_t skipped)
>>> @@ -275,7 +297,11 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>>>    	struct cxl_port *port = cxled_to_port(cxled);
>>>    	struct cxl_dev_state *cxlds = cxlmd->cxlds;
>>>    	struct device *dev = &port->dev;
>>> +	struct device *ed_dev = &cxled->cxld.dev;
>>> +	struct resource *dpa_res = &cxlds->dpa_res;
>>> +	resource_size_t skip_len = 0;
>>>    	struct resource *res;
>>> +	int rc, index;
>>>    
>>>    	lockdep_assert_held_write(&cxl_dpa_rwsem);
>>>    
>>> @@ -304,28 +330,119 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>>>    	}
>>>    
>>>    	if (skipped) {
>>> -		res = __request_region(&cxlds->dpa_res, base - skipped, skipped,
>>> -				       dev_name(&cxled->cxld.dev), 0);
>>> -		if (!res) {
>>> -			dev_dbg(dev,
>>> -				"decoder%d.%d: failed to reserve skipped space\n",
>>> -				port->id, cxled->cxld.id);
>>> -			return -EBUSY;
>>> +		resource_size_t skip_base = base - skipped;
>>> +
>>> +		if (decoder_mode_is_dc(cxled->mode)) {
>>
>> Maybe move this entire block to a helper function to reduce the size of
>> the current function and reduce indent levels and improve readability?
> 
> :-/
> 
> I'll work on breaking it out more.  The logic here is getting kind of
> crazy.
> 
>>
>>> +			if (resource_size(&cxlds->ram_res) &&
>>> +					skip_base <= cxlds->ram_res.end) {
>>> +				skip_len = cxlds->ram_res.end - skip_base + 1;
>>> +				res = __request_region(dpa_res, skip_base,
>>> +						skip_len, dev_name(ed_dev), 0);
>>> +				if (!res)
>>> +					goto error;
>>> +
>>> +				rc = xa_insert(&cxled->skip_res, skip_base, res,
>>> +								GFP_KERNEL);
>>> +				skip_base += skip_len;
>>> +			}
>>> +
>>> +			if (resource_size(&cxlds->ram_res) &&
>                                                    ^^^^^^^
> 						  pmem_res?
> 
>>> +					skip_base <= cxlds->pmem_res.end) {
> 
> The 2 if statements here are almost exactly the same.  To the point I
> wonder if there is a bug.
> 
> Navneet,
> 
> Why does the code check ram_res the second time but go on to use pmem_res
> in the block?
> 
>>> +				skip_len = cxlds->pmem_res.end - skip_base + 1;
>>> +				res = __request_region(dpa_res, skip_base,
>>> +						skip_len, dev_name(ed_dev), 0);
>>> +				if (!res)
>>> +					goto error;
>>> +
>>> +				rc = xa_insert(&cxled->skip_res, skip_base, res,
>>> +								GFP_KERNEL);
>>> +				skip_base += skip_len;
>>> +			}
>>> +
>>> +			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;
>>> +					res = __request_region(dpa_res,
>>> +							skip_base, skip_len,
>>> +							dev_name(ed_dev), 0);
>>> +					if (!res)
>>> +						goto error;
>>> +
>>> +					rc = xa_insert(&cxled->skip_res, skip_base,
>>> +							res, GFP_KERNEL);
>>> +					skip_base += skip_len;
>>> +				}
>>> +
>>> +				if (skip_base == base) {
>>> +					dev_dbg(dev, "skip done!\n");
>>> +					break;
>>> +				}
>>> +
>>> +				if (resource_size(dcr) &&
>>> +						skip_base <= dcr->end) {
>>> +					if (skip_base > base)
>>> +						dev_err(dev, "Skip error\n");
>>> +
>>> +					skip_len = dcr->end - skip_base + 1;
>>> +					res = __request_region(dpa_res, skip_base,
>>> +							skip_len,
>>> +							dev_name(ed_dev), 0);
>>> +					if (!res)
>>> +						goto error;
>>> +
>>> +					rc = xa_insert(&cxled->skip_res, skip_base,
>>> +							res, GFP_KERNEL);
>>> +					skip_base += skip_len;
>>> +				}
>>> +			}
>>> +		} else	{
>>> +			res = __request_region(dpa_res, base - skipped, skipped,
>>> +							dev_name(ed_dev), 0);
>>> +			if (!res)
>>> +				goto error;
>>> +
>>> +			rc = xa_insert(&cxled->skip_res, skip_base, res,
>>> +								GFP_KERNEL);
>>>    		}
>>>    	}
>>> -	res = __request_region(&cxlds->dpa_res, base, len,
>>> -			       dev_name(&cxled->cxld.dev), 0);
>>> +
>>> +	res = __request_region(dpa_res, base, len, dev_name(ed_dev), 0);
>>>    	if (!res) {
>>>    		dev_dbg(dev, "decoder%d.%d: failed to reserve allocation\n",
>>> -			port->id, cxled->cxld.id);
>>> -		if (skipped)
>>> -			__release_region(&cxlds->dpa_res, base - skipped,
>>> -					 skipped);
>>> +				port->id, cxled->cxld.id);
>>> +		if (skipped) {
>>> +			resource_size_t skip_base = base - skipped;
>>> +
>>> +			while (skipped != 0) {
>>> +				if (skip_base > base)
>>> +					dev_err(dev, "Skip error\n");
>>> +
>>> +				res = xa_load(&cxled->skip_res, skip_base);
>>> +				__release_region(dpa_res, skip_base,
>>> +							resource_size(res));
>>> +				xa_erase(&cxled->skip_res, skip_base);
>>> +				skip_base += resource_size(res);
>>> +				skipped -= resource_size(res);
>>> +			}
>>> +		}
>>>    		return -EBUSY;
>>>    	}
>>>    	cxled->dpa_res = res;
>>>    	cxled->skip = skipped;
>>>    
>>> +	for (int mode = CXL_DECODER_DC0; mode <= CXL_DECODER_DC7; mode++) {
>>> +		int index = dc_mode_to_region_index(mode);
>>> +
>>> +		if (resource_contains(&cxlds->dc_res[index], res)) {
>>> +			cxled->mode = mode;
>>> +			dev_dbg(dev, "decoder%d.%d: %pr mode: %d\n", port->id,
>>> +				cxled->cxld.id, cxled->dpa_res, cxled->mode);
>>> +			goto success > +		}
>>> +	}
>>
>> This block should only happen if decoder_mode_is_dc() right? If that's
>> the case, you might be able to refactor it so the 'goto success' isn't
>> necessary.
> 
> I'll check.  I looked through this code a couple of times in my review
> before posting because I'm not 100% sure I want to see 8 different modes
> DC decoders and regions.
> 
> I think the 'mode' should be 'DC' with an index in the endpoint decoder to
> map DC region that decoder is mapping.  But that change was much bigger to
> Navneets code and I wanted to see how others felt about having DC0 - DC7
> modes.  My compromise was creating decoder_mode_is_dc().
> 
>>
>>>    	if (resource_contains(&cxlds->pmem_res, res))
>>>    		cxled->mode = CXL_DECODER_PMEM;
>>>    	else if (resource_contains(&cxlds->ram_res, res))
>>> @@ -336,9 +453,16 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>>>    		cxled->mode = CXL_DECODER_MIXED;
>>>    	}
>>>    
>>> +success:
>>>    	port->hdm_end++;
>>>    	get_device(&cxled->cxld.dev);
>>>    	return 0;
>>> +
>>> +error:
>>> +	dev_dbg(dev, "decoder%d.%d: failed to reserve skipped space\n",
>>> +			port->id, cxled->cxld.id);
>>> +	return -EBUSY;
>>> +
>>>    }
>>>    
>>>    int devm_cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>>> @@ -429,6 +553,14 @@ int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled,
>>>    	switch (mode) {
>>>    	case CXL_DECODER_RAM:
>>>    	case CXL_DECODER_PMEM:
>>> +	case CXL_DECODER_DC0:
>>> +	case CXL_DECODER_DC1:
>>> +	case CXL_DECODER_DC2:
>>> +	case CXL_DECODER_DC3:
>>> +	case CXL_DECODER_DC4:
>>> +	case CXL_DECODER_DC5:
>>> +	case CXL_DECODER_DC6:
>>> +	case CXL_DECODER_DC7:
> 
> For example this seems very hacky...

Not sure if it helps, but you can always do:
case CXL_DECODER_DC0 ... CXL_DECODER_DC7:

DJ

> 
> [snip]
> 
>>>    
>>> +/*
>>> + * The region can not be manged by CXL if any portion of
>>> + * it is already online as 'System RAM'
>>> + */
>>> +static bool region_is_system_ram(struct cxl_region *cxlr,
>>> +				 struct cxl_region_params *p)
>>> +{
>>> +	return (walk_iomem_res_desc(IORES_DESC_NONE,
>>> +				    IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
>>> +				    p->res->start, p->res->end, cxlr,
>>> +				    is_system_ram) > 0);
>>> +}
>>> +
>>>    static int cxl_region_probe(struct device *dev)
>>>    {
>>>    	struct cxl_region *cxlr = to_cxl_region(dev);
>>> @@ -3174,14 +3287,7 @@ static int cxl_region_probe(struct device *dev)
>>>    	case CXL_DECODER_PMEM:
>>>    		return devm_cxl_add_pmem_region(cxlr);
>>>    	case CXL_DECODER_RAM:
>>> -		/*
>>> -		 * The region can not be manged by CXL if any portion of
>>> -		 * it is already online as 'System RAM'
>>> -		 */
>>> -		if (walk_iomem_res_desc(IORES_DESC_NONE,
>>> -					IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
>>> -					p->res->start, p->res->end, cxlr,
>>> -					is_system_ram) > 0)
>>> +		if (region_is_system_ram(cxlr, p))
>>
>> Maybe split this change out as a prep patch before the current patch.
> 
> That seems reasonable.  But the patch is not so large and the
> justification for creating a helper is that we need this same check for DC
> regions.  So it seemed ok to leave it like this.  Let me see about
> splitting it out.
> 
> [snip]
> 
>>> diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c
>>> index ccdf8de85bd5..eb5eb81bfbd7 100644
>>> --- a/drivers/dax/cxl.c
>>> +++ b/drivers/dax/cxl.c
>>> @@ -23,11 +23,15 @@ static int cxl_dax_region_probe(struct device *dev)
>>>    	if (!dax_region)
>>>    		return -ENOMEM;
>>>    
>>> +	if (decoder_mode_is_dc(cxlr->mode))
>>> +		return 0;
>>> +
>>>    	data = (struct dev_dax_data) {
>>>    		.dax_region = dax_region,
>>>    		.id = -1,
>>>    		.size = range_len(&cxlr_dax->hpa_range),
>>>    	};
>>> +
>>
>> Stray blank line?
> 
> Opps!  Fixed!
> 
> Ira