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

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Date:   Sat, 18 Feb 2023 03:17:58 +0000
From:   "Verma, Vishal L" <vishal.l.verma@...el.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>,
        "Schofield, Alison" <alison.schofield@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "bwidawsk@...nel.org" <bwidawsk@...nel.org>,
        "Weiny, Ira" <ira.weiny@...el.com>
CC:     "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cxl/hdm: dev_warn() on unsupported mixed mode decoder

On Fri, 2023-02-17 at 17:38 -0800, 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>
> ---
>  drivers/cxl/core/hdm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Looks good,
Reviewed-by: Vishal Verma <vishal.l.verma@...el.com>

> 
> 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