linux-kernel - Re: [PATCH] cxl: Fix premature commit_end increment on decoder commit failure

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Message-ID: <aXudN_vAy7frUcWM@aschofie-mobl2.lan>
Date: Thu, 29 Jan 2026 09:47:35 -0800
From: Alison Schofield <alison.schofield@...el.com>
To: Yuxiong Wang <yuxiong.wang@...ux.alibaba.com>
CC: <dave@...olabs.net>, <jonathan.cameron@...wei.com>,
	<dave.jiang@...el.com>, <vishal.l.verma@...el.com>, <ira.weiny@...el.com>,
	<dan.j.williams@...el.com>, <ming.li@...omail.com>, <rrichter@....com>,
	<linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Huang Ying
	<ying.huang@...ux.alibaba.com>
Subject: Re: [PATCH] cxl: Fix premature commit_end increment on decoder
 commit failure

On Thu, Jan 29, 2026 at 02:45:52PM +0800, Yuxiong Wang wrote:
> In cxl_decoder_commit(), commit_end is incremented before verifying whether the
> commit succeeded, and the CXL_DECODER_F_ENABLE bit in cxld->flags is only set
> after a successful commit. As a result, if the commit fails, commit_end has been
> incremented and cxld->reset() has no effect since the flag is not set, so commit_end
> remains incorrectly incremented. The inconsistency between commit_end and
> CXL_DECODER_F_ENABLE causes failure during subsequent either commit or reset
> operations.
> 
> Fix this by incrementing commit_end only after confirming the commit succeeded.
> Also, remove the ineffective cxld->reset() call. According to CXL 3.2 Spec 8.2.4.20.12

DaveJ - Maybe s/3.2/4.0 above on applying please.

It's the same section either way but lets encourage new references to use the
latest version of CXL Spec.


> Committing Decoder Programming, since cxld_await_commit() has cleared the decoder
> commit bit on failure, no additional reset is required.
> 
> Fixes: 176baef ("cxl/hdm: Commit decoder state to hardware")
> Signed-off-by: Yuxiong Wang <yuxiong.wang@...ux.alibaba.com>
> Acked-by: Huang Ying <ying.huang@...ux.alibaba.com>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> Reviewed-by: Alison Schofield <alison.schofield@...el.com>
> ---
> Change log:
>  * Added CXL 3.2 Spec 8.2.4.20.12 Committing Decoder Programming statement. Thanks
>    Alison.
>  * Collected reviewed-by. Thanks Dave and Alison.
> RFC Link: https://lore.kernel.org/linux-cxl/aXqKC-bscufh1ggq@aschofie-mobl2.lan/
> ---
>  drivers/cxl/core/hdm.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index eb5a3a7640c6..912f648a6b7a 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -844,14 +844,13 @@ static int cxl_decoder_commit(struct cxl_decoder *cxld)
>  	scoped_guard(rwsem_read, &cxl_rwsem.dpa)
>  		setup_hw_decoder(cxld, hdm);
>  
> -	port->commit_end++;
>  	rc = cxld_await_commit(hdm, cxld->id);
>  	if (rc) {
>  		dev_dbg(&port->dev, "%s: error %d committing decoder\n",
>  			dev_name(&cxld->dev), rc);
> -		cxld->reset(cxld);
>  		return rc;
>  	}
> +	port->commit_end++;
>  	cxld->flags |= CXL_DECODER_F_ENABLE;
>  
>  	return 0;
> -- 
> 2.50.1 (Apple Git-155)
>