Re: [NDCTL PATCH v6 3/4] ndctl: cxl: add QoS class check for CXL region creation

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

On 2/7/24 2:02 PM, Verma, Vishal L wrote:
> On Wed, 2024-02-07 at 10:19 -0700, Dave Jiang wrote:
>> The CFMWS provides a QTG ID. The kernel driver creates a root decoder that
>> represents the CFMWS. A qos_class attribute is exported via sysfs for the root
>> decoder.
>>
>> One or more QoS class tokens are retrieved via QTG ID _DSM from the ACPI0017
>> device for a CXL memory device. The input for the _DSM is the read and write
>> latency and bandwidth for the path between the device and the CPU. The
>> numbers are constructed by the kernel driver for the _DSM input. When a
>> device is probed, QoS class tokens  are retrieved. This is useful for a
>> hot-plugged CXL memory device that does not have regions created.
>>
>> Add a QoS check during region creation. Emit a warning if the qos_class
>> token from the root decoder is different than the mem device qos_class
>> token. User parameter options are provided to fail instead of just
>> warning.
>>
>> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
>> ---
>> v6:
>> - Check return value of create_region_validate_qos_class() (Wonjae)
>> ---
>>  Documentation/cxl/cxl-create-region.txt |  9 ++++
>>  cxl/region.c                            | 58 ++++++++++++++++++++++++-
>>  2 files changed, 66 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/cxl/cxl-create-region.txt b/Documentation/cxl/cxl-create-region.txt
>> index f11a412bddfe..d5e34cf38236 100644
>> --- a/Documentation/cxl/cxl-create-region.txt
>> +++ b/Documentation/cxl/cxl-create-region.txt
>> @@ -105,6 +105,15 @@ include::bus-option.txt[]
>>  	supplied, the first cross-host bridge (if available), decoder that
>>  	supports the largest interleave will be chosen.
>>  
>> +-e::
>> +--strict::
>> +	Enforce strict execution where any potential error will force failure.
>> +	For example, if qos_class mismatches region creation will fail.
>> +
>> +-q::
>> +--no-enforce-qos::
>> +	Parameter to bypass qos_class mismatch failure. Will only emit warning.
> 
> Hm, -q is usually synonymous with --quiet, it might be nice to reserve
> it for that in case we ever need to add a quiet mode. Maybe use -Q?

Sure. I'll change it. 
> 
> 
>