netdev - Re: [PATCH v5 22/27] cxl: allow region creation by type2 drivers

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Message-ID: <904b31b1-ee0a-542c-a99a-8a5ca38bec77@amd.com>
Date: Wed, 20 Nov 2024 13:51:39 +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
Subject: Re: [PATCH v5 22/27] cxl: allow region creation by type2 drivers


On 11/19/24 20:37, Zhi Wang wrote:
> On Mon, 18 Nov 2024 16:44:29 +0000
> <alejandro.lucero-palau@....com> wrote:
>
>> From: Alejandro Lucero <alucerop@....com>
>>
<snip>
>>   
>> -/* 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)
>> +static void construct_region_end(void)
>> +{
>> +	up_write(&cxl_region_rwsem);
>> +}
>> +
>> +static struct cxl_region *construct_region_begin(struct cxl_root_decoder *cxlrd,
>> +						 struct cxl_endpoint_decoder *cxled)
>>   {
>>   	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
>> -	struct cxl_port *port = cxlrd_to_port(cxlrd);
>> -	struct range *hpa = &cxled->cxld.hpa_range;
>>   	struct cxl_region_params *p;
>>   	struct cxl_region *cxlr;
>> -	struct resource *res;
>> -	int rc;
>> +	int err;
> maybe let's keep the original name "rc".


Note this is a new function. It comes straight from original Dan's 
patch, and I think he changed that as there is another function doing 
the "return call" which invokes this one as part of the call.


>>   
>>   	do {
>>   		cxlr = __create_region(cxlrd, cxled->mode,
>> @@ -3395,8 +3416,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>>   	} while (IS_ERR(cxlr) && PTR_ERR(cxlr) == -EBUSY);
>>   
>>   	if (IS_ERR(cxlr)) {
>> -		dev_err(cxlmd->dev.parent,
>> -			"%s:%s: %s failed assign region: %ld\n",
>> +		dev_err(cxlmd->dev.parent, "%s:%s: %s failed assign region: %ld\n",
>>   			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
>>   			__func__, PTR_ERR(cxlr));
>>   		return cxlr;
>> @@ -3406,13 +3426,33 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>>   	p = &cxlr->params;
>>   	if (p->state >= CXL_CONFIG_INTERLEAVE_ACTIVE) {
>>   		dev_err(cxlmd->dev.parent,
>> -			"%s:%s: %s autodiscovery interrupted\n",
>> +			"%s:%s: %s region setup interrupted\n",
>>   			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
>>   			__func__);
>> -		rc = -EBUSY;
>> -		goto err;
>> +		err = -EBUSY;
>> +		construct_region_end();
>> +		drop_region(cxlr);
>> +		return ERR_PTR(err);
>>   	}
>>   
>> +	return cxlr;
>> +}
>> +
>> +/* 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)
>> +{
>> +	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
>> +	struct range *hpa = &cxled->cxld.hpa_range;
>> +	struct cxl_region_params *p;
>> +	struct cxl_region *cxlr;
>> +	struct resource *res;
>> +	int rc;
>> +
>> +	cxlr = construct_region_begin(cxlrd, cxled);
>> +	if (IS_ERR(cxlr))
>> +		return cxlr;
>> +
>>   	set_bit(CXL_REGION_F_AUTO, &cxlr->flags);
>>   
>>   	res = kmalloc(sizeof(*res), GFP_KERNEL);
>> @@ -3435,6 +3475,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>>   			 __func__, dev_name(&cxlr->dev));
>>   	}
>>   
>> +	p = &cxlr->params;
>>   	p->res = res;
>>   	p->interleave_ways = cxled->cxld.interleave_ways;
>>   	p->interleave_granularity = cxled->cxld.interleave_granularity;
>> @@ -3452,15 +3493,91 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>>   	/* ...to match put_device() in cxl_add_to_region() */
>>   	get_device(&cxlr->dev);
>>   	up_write(&cxl_region_rwsem);
>> -
>> +	construct_region_end();
> cxl_region_rwsem seems got up_write() two times. Guess you should remove
> it like below since it is now done in construct_region_end().



You are right. I think I messed up that with the code below for handling 
a potential error.

I'll fix it.

Good catch!


>>   	return cxlr;
>>   
>>   err:
>> -	up_write(&cxl_region_rwsem);
>> -	devm_release_action(port->uport_dev, unregister_region, cxlr);
>> +	construct_region_end();
>> +	drop_region(cxlr);
>> +	return ERR_PTR(rc);
>> +}
>> +