netdev - Re: [PATCH v3 18/20] cxl: preclude device memory to be used for dax

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Message-ID: <fd540034-2dcf-2f36-916f-1e8f1e091462@amd.com>
Date: Mon, 16 Sep 2024 15:32:33 +0100
From: Alejandro Lucero Palau <alucerop@....com>
To: Dave Jiang <dave.jiang@...el.com>, alejandro.lucero-palau@....com,
 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 v3 18/20] cxl: preclude device memory to be used for dax


On 9/13/24 18:26, Dave Jiang wrote:
>
> On 9/7/24 1:18 AM, alejandro.lucero-palau@....com wrote:
>> From: Alejandro Lucero <alucerop@....com>
>>
>> By definition a type2 cxl device will use the host managed memory for
>> specific functionality, therefore it should not be available to other
>> uses.
>>
>> Signed-off-by: Alejandro Lucero <alucerop@....com>
>> ---
>>   drivers/cxl/core/region.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index d8c29e28e60c..45b4891035a6 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -3699,6 +3699,9 @@ static int cxl_region_probe(struct device *dev)
>>   	case CXL_DECODER_PMEM:
>>   		return devm_cxl_add_pmem_region(cxlr);
>>   	case CXL_DECODER_RAM:
>> +		if (cxlr->type != CXL_DECODER_HOSTONLYMEM)
>> +			return 0;
>> +
> While it's highly unlikely that someone puts pmem on a type2 device, the spec does not forbid it. Maybe it makes sense to just return 0 above this switch block entirely and skip this code block?


Yes, it makes sense.

I'll do it.

Thanks


>
>>   		/*
>>   		 * The region can not be manged by CXL if any portion of
>>   		 * it is already online as 'System RAM'