Re: [PATCH v4 4/4] cxl/hdm: Restore commit_end when decoder enumeration fails

On 7/20/26 6:59 PM, Alison Schofield wrote:
> commit_end tracks the highest committed decoder on a port. It gets
> advanced before decoder enumeration is complete, so a later failure
> leaves it pointing at a decoder that was never added. The next probe
> then rejects decoder0 as out of order and enumeration fails.
> 
> Reset commit_end to the none committed baseline once the decoders are

s/none committed/uncommitted/ ?

> torn down, so a subsequent probe rebuilds it from scratch. Register
> the reset before the decoders are added so that on unwind it runs
> after every decoder has been unregistered. This prevents commit_end
> from dropping below the highest committed decoder still registered and
> exposing an inconsistent value to a concurrent reader.
> 
> Protect the commit_end advance in the DVSEC emulation path against
> concurrent readers, matching the register-programmed path.
> 
> Fixes: 176baefb2eb5 ("cxl/hdm: Commit decoder state to hardware")
> Fixes: b777e9bec960 ("cxl/hdm: Emulate HDM decoder from DVSEC range registers")
> Signed-off-by: Alison Schofield <[email protected]>

Reviewed-by: Dave Jiang <[email protected]>


> ---
>  drivers/cxl/core/hdm.c | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 077aface1a2a..7d4ba7fa30fa 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -955,7 +955,8 @@ static int cxl_setup_hdm_decoder_from_dvsec(
>  	 * change the range registers at run time.
>  	 */
>  	cxld->flags |= CXL_DECODER_F_ENABLE | CXL_DECODER_F_LOCK;
> -	port->commit_end = cxld->id;
> +	scoped_guard(rwsem_write, &cxl_rwsem.region)
> +		port->commit_end = cxld->id;
>  
>  	rc = devm_cxl_dpa_reserve(cxled, *dpa_base, len, 0);
>  	if (rc) {
> @@ -1181,6 +1182,14 @@ static void cxl_settle_decoders(struct cxl_hdm *cxlhdm)
>  		msleep(20);
>  }
>  
> +static void cxl_reset_commit_end(void *data)
> +{
> +	struct cxl_port *port = data;
> +
> +	guard(rwsem_write)(&cxl_rwsem.region);
> +	port->commit_end = -1;
> +}
> +
>  /**
>   * devm_cxl_enumerate_decoders - add decoder objects per HDM register set
>   * @cxlhdm: Structure to populate with HDM capabilities
> @@ -1191,13 +1200,21 @@ static int devm_cxl_enumerate_decoders(struct cxl_hdm *cxlhdm,
>  {
>  	void __iomem *hdm = cxlhdm->regs.hdm_decoder;
>  	struct cxl_port *port = cxlhdm->port;
> -	int i;
>  	u64 dpa_base = 0;
> +	int i, rc;
>  
>  	cxl_settle_decoders(cxlhdm);
>  
> +	/*
> +	 * Reset commit_end after all decoders have been torn down so a
> +	 * subsequent probe rebuilds it from scratch.
> +	 */
> +	rc = devm_add_action(&port->dev, cxl_reset_commit_end, port);
> +	if (rc)
> +		return rc;
> +
>  	for (i = 0; i < cxlhdm->decoder_count; i++) {
> -		int rc, target_count = cxlhdm->target_count;
> +		int target_count = cxlhdm->target_count;
>  		struct cxl_decoder *cxld;
>  
>  		if (is_cxl_endpoint(port)) {