linux-kernel - Re: [PATCH] cxl/hdm: dev_warn() on unsupported mixed mode decoder

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Message-ID: <5fc5d37d-e65a-10db-14c4-91f3a99fca91@intel.com>
Date:   Tue, 21 Feb 2023 10:14:06 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     alison.schofield@...el.com,
        Dan Williams <dan.j.williams@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>
Cc:     linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cxl/hdm: dev_warn() on unsupported mixed mode decoder



On 2/17/23 6:38 PM, alison.schofield@...el.com wrote:
> From: Alison Schofield <alison.schofield@...el.com>
> 
> A mixed mode decoder is programmed with device physical addresses
> that span both ram and pmem partitions of a memdev.
> 
> Linux does not support mixed mode decoders. The driver rejects
> sysfs writes that try to set decoder mode to mixed, and if a
> resource bieng allocated is not wholly contained in either the
> pmem or ram partition of a memdev, it is also rejected. Basically,
> the CXL region driver is not going to create regions with mixed
> mode decoders, but the BIOS could.
> 
> If the kernel driver sees the mixed mode decoder, it will fail to
> enable the region, and emit a dev_dbg() message.
> 
> A dev_dbg() is not noisy enough in this case. Change the message
> to be a dev_warn() that explicitly says mixed mode is not supported.
> 
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Alison Schofield <alison.schofield@...el.com>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>

> ---
>   drivers/cxl/core/hdm.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 45deda18ed32..9eaf93c8ebb0 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -294,8 +294,8 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>   	else if (resource_contains(&cxlds->ram_res, res))
>   		cxled->mode = CXL_DECODER_RAM;
>   	else {
> -		dev_dbg(dev, "decoder%d.%d: %pr mixed\n", port->id,
> -			cxled->cxld.id, cxled->dpa_res);
> +		dev_warn(dev, "decoder%d.%d: %pr mixed mode not supported\n",
> +			 port->id, cxled->cxld.id, cxled->dpa_res);
>   		cxled->mode = CXL_DECODER_MIXED;
>   	}
>   
> 
> base-commit: a5fcd228ca1db9810ba1ed461c90b6ee933b9daf