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

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Message-ID: <Zvv_23tPL_1XZlmv@PC2K9PVX.TheFacebook.com>
Date: Tue, 1 Oct 2024 09:57:47 -0400
From: Gregory Price <gourry@...rry.net>
To: Huang Ying <ying.huang@...el.com>
Cc: Dan Williams <dan.j.williams@...el.com>,
	Dave Jiang <dave.jiang@...el.com>, linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org, Davidlohr Bueso <dave@...olabs.net>,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Alison Schofield <alison.schofield@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	Alejandro Lucero <alucerop@....com>
Subject: Re: [RFC 5/5] cxl: Avoid to create dax regions for type2 accelerators

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@dwillia2-xfh.jf.intel.com.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@dwillia2-xfh.jf.intel.com/
> 
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Co-developed-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> Cc: Davidlohr Bueso <dave@...olabs.net>
> Cc: Jonathan Cameron <jonathan.cameron@...wei.com>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Alison Schofield <alison.schofield@...el.com>
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Alejandro Lucero <alucerop@....com>
> ---
>  drivers/cxl/core/region.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 

Reviewed-by: Gregory Price <gourry@...rry.net>

> 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
>