netdev - Re: [PATCH v14 19/22] cxl: add region flag for precluding a device memory to be used for dax

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Message-ID: <6a341a58-5d07-4f1c-9680-b04030ecb172@amd.com>
Date: Fri, 9 May 2025 09:16:28 +0100
From: Alejandro Lucero Palau <alucerop@....com>
To: Alison Schofield <alison.schofield@...el.com>,
 alejandro.lucero-palau@....com
Cc: linux-cxl@...r.kernel.org, netdev@...r.kernel.org,
 dan.j.williams@...el.com, edward.cree@....com, davem@...emloft.net,
 kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com,
 dave.jiang@...el.com, Zhi Wang <zhiw@...dia.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Ben Cheatham <benjamin.cheatham@....com>
Subject: Re: [PATCH v14 19/22] cxl: add region flag for precluding a device
 memory to be used for dax


On 5/8/25 19:20, Alison Schofield wrote:
> On Thu, Apr 17, 2025 at 10:29:22PM +0100, 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. However, a dax interface could be just good enough in some cases.
>>
>> Add a flag to a cxl region for specifically state to not create a dax
>> device. Allow a Type2 driver to set that flag at region creation time.
>>
>> Signed-off-by: Alejandro Lucero <alucerop@....com>
>> Reviewed-by: Zhi Wang <zhiw@...dia.com>
>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>> Reviewed-by: Ben Cheatham <benjamin.cheatham@....com>
>> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
>> ---
>>   drivers/cxl/core/region.c | 10 +++++++++-
>>   drivers/cxl/cxl.h         |  3 +++
>>   include/cxl/cxl.h         |  3 ++-
>>   3 files changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index f55fb253ecde..cec168a26efb 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -3649,12 +3649,14 @@ __construct_new_region(struct cxl_root_decoder *cxlrd,
>>    * @cxlrd: root decoder to allocate HPA
>>    * @cxled: endpoint decoder with reserved DPA capacity
>>    * @ways: interleave ways required
>> + * @no_dax: if true no DAX device should be created
> I'll suggest avoiding the double negative on no_dax and name this
> variable based on what can happen, not what must be prevented.
>
> Something like: dax_allowed or allow_dax or dax_ok
>

Not sure about this one.


IMO, being negative implies not to do the default action, as an 
exception, and it reflects better the point.