Re: [RFC 5/5] cxl: Avoid to create dax regions for type2 accelerators

[Gregory Price]

On Wed, Sep 25, 2024 at 10:46:47AM +0800, Huang Ying wrote:
> The memory range of a type2 accelerator should be managed by the type2
> accelerator specific driver instead of the common dax region drivers,
> as discussed in [1].
> 
> [1] https://lore.kernel.org/linux-cxl/66469ff1b8fbc_2c2629427@xxxxxxxxxxxxxxxxxxxxxxxxx.notmuch/
> 
> So, in this patch, we skip dax regions creation for type2 accelerator
> device memory regions.
> 
> Based on: https://lore.kernel.org/linux-cxl/168592159835.1948938.1647215579839222774.stgit@xxxxxxxxxxxxxxxxxxxxxxxxx/
> 
> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Co-developed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> Cc: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Alison Schofield <alison.schofield@xxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Cc: Alejandro Lucero <alucerop@xxxxxxx>
> ---
>  drivers/cxl/core/region.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 

Reviewed-by: Gregory Price <gourry@xxxxxxxxxx>

> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 9c68ec445128..b276752c38da 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3466,6 +3466,14 @@ static int cxl_region_probe(struct device *dev)
>  					p->res->start, p->res->end, cxlr,
>  					is_system_ram) > 0)
>  			return 0;
> +		/*
> +		 * Accelerator regions have specific usage, skip
> +		 * device-dax registration.
> +		 */
> +		if (cxlr->type == CXL_DECODER_ACCEL)
> +			return 0;
> +
> +		/* Expander routes to device-dax */
>  		return devm_cxl_add_dax_region(cxlr);
>  	default:
>  		dev_dbg(&cxlr->dev, "unsupported region mode: %d\n",
> -- 
> 2.39.2
>