netdev - Re: [PATCH v6 26/28] cxl: add function for obtaining region range

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Message-ID: <57793990-1350-de8a-efc5-86dee5b215e2@amd.com>
Date: Mon, 9 Dec 2024 09:48:01 +0000
From: Alejandro Lucero Palau <alucerop@....com>
To: Zhi Wang <zhiw@...dia.com>, alejandro.lucero-palau@....com
Cc: linux-cxl@...r.kernel.org, netdev@...r.kernel.org,
 dan.j.williams@...el.com, martin.habets@...inx.com, edward.cree@....com,
 davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
 edumazet@...gle.com, dave.jiang@...el.com
Subject: Re: [PATCH v6 26/28] cxl: add function for obtaining region range


On 12/3/24 18:53, Zhi Wang wrote:
> On Mon, 2 Dec 2024 17:12:20 +0000
> <alejandro.lucero-palau@....com> wrote:
>
>> From: Alejandro Lucero <alucerop@....com>
>>
>> A CXL region struct contains the physical address to work with.
>>
>> Add a function for getting the cxl region range to be used for mapping
>> such memory range.
>>
>> Signed-off-by: Alejandro Lucero <alucerop@....com>
>> ---
>>   drivers/cxl/core/region.c | 15 +++++++++++++++
>>   drivers/cxl/cxl.h         |  1 +
>>   include/cxl/cxl.h         |  1 +
>>   3 files changed, 17 insertions(+)
>>
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index 5cb7991268ce..021e9b373cdd 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -2667,6 +2667,21 @@ static struct cxl_region *devm_cxl_add_region(struct cxl_root_decoder *cxlrd,
>>   	return ERR_PTR(rc);
>>   }
>>   
>> +int cxl_get_region_range(struct cxl_region *region, struct range *range)
>> +{
>> +	if (!region)
>> +		return -ENODEV;
>> +
> I am leaning towards having a WARN_ON_ONCE() above.
>

Not sure. The call is quite simple and to check the error should be 
enough for understanding what is going on.

In this case any error implies a problem with a previous call when 
creating the region which was not likely checked for errors.

And if a log is necessary, I think a WARN_ON should be used instead.


>> +	if (!region->params.res)
>> +		return -ENOSPC;
>> +
>> +	range->start = region->params.res->start;
>> +	range->end = region->params.res->end;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_get_region_range, CXL);
>> +
>>   static ssize_t __create_region_show(struct cxl_root_decoder *cxlrd, char *buf)
>>   {
>>   	return sysfs_emit(buf, "region%u\n", atomic_read(&cxlrd->region_id));
>> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
>> index cc9e3d859fa6..32d2bd0520d4 100644
>> --- a/drivers/cxl/cxl.h
>> +++ b/drivers/cxl/cxl.h
>> @@ -920,6 +920,7 @@ void cxl_coordinates_combine(struct access_coordinate *out,
>>   
>>   bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
>>   
>> +int cxl_get_region_range(struct cxl_region *region, struct range *range);
>>   /*
>>    * Unit test builds overrides this to __weak, find the 'strong' version
>>    * of these symbols in tools/testing/cxl/.
>> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
>> index 14be26358f9c..0ed9e32f25dd 100644
>> --- a/include/cxl/cxl.h
>> +++ b/include/cxl/cxl.h
>> @@ -65,4 +65,5 @@ struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
>>   				     bool no_dax);
>>   
>>   int cxl_accel_region_detach(struct cxl_endpoint_decoder *cxled);
>> +int cxl_get_region_range(struct cxl_region *region, struct range *range);
>>   #endif