Re: [PATCH 10/17] cxl/cache, mem: Prevent RAS register mapping race

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Tue, 11 Nov 2025 15:40:25 -0600
Ben Cheatham <Benjamin.Cheatham@amd.com> wrote:

> CXL type 2 devices will register both a struct cxl_memdev and struct
> cxl_cachedev, both of which will attempt to map the parent dport's RAS
> registers in cxl_dport_init_ras_reporting(). While the immediate call
> fails gracefully, an error is emitted in the dmesg log by
> cxl_map_component_regs().
> 
> Avoid this error message by checking if the RAS registers are already
> mapped while the port's device lock is held.

This seems misleading. The check seems to be one whether
cdlds->cxlmd or cxlcd have already been configured rather than
just the RAS registers.

> 
> Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
> ---
>  drivers/cxl/cache.c | 11 +++++++++++
>  drivers/cxl/mem.c   |  5 +++--
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/cache.c b/drivers/cxl/cache.c
> index 630452d53acc..4c9280c0ea72 100644
> --- a/drivers/cxl/cache.c
> +++ b/drivers/cxl/cache.c
> @@ -58,6 +58,7 @@ static int cxl_cache_probe(struct device *dev)
>  {
>  	struct cxl_cachedev *cxlcd = to_cxl_cachedev(dev);
>  	struct cxl_dev_state *cxlds = cxlcd->cxlds;
> +	struct device *endpoint_parent;
>  	struct cxl_dport *dport;
>  	int rc;
>  
> @@ -72,6 +73,16 @@ static int cxl_cache_probe(struct device *dev)
>  		return -ENXIO;
>  	}
>  
> +	if (dport->rch)
> +		endpoint_parent = parent_port->uport_dev;
> +	else
> +		endpoint_parent = &parent_port->dev;
> +
> +	scoped_guard(device, endpoint_parent) {
> +		if (!cxlds->cxlmd)
> +			cxl_dport_init_ras_reporting(dport, dev);
> +	}
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index 3b230f8c5925..35706ec1b7e1 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -129,9 +129,10 @@ static int cxl_mem_probe(struct device *dev)
>  	else
>  		endpoint_parent = &parent_port->dev;
>  
> -	cxl_dport_init_ras_reporting(dport, dev);
> -
>  	scoped_guard(device, endpoint_parent) {
> +		if (!cxlds->cxlcd)
> +			cxl_dport_init_ras_reporting(dport, dev);
> +
>  		if (!endpoint_parent->driver) {
>  			dev_err(dev, "CXL port topology %s not enabled\n",
>  				dev_name(endpoint_parent));