Re: [PATCH v7 1/2 RESEND] cxl/hdm: Allow zero sized HDM decoders

On Tue, Jul 21, 2026 at 09:16:24AM +0800, [email protected] wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] cxl_dpa_free() returns early for zero-sized decoders, bypassing resource release, leaking the DPA reservation, and permanently breaking port LIFO teardown.
> --
> 
> --- Patch [1]: [PATCH v7 1/2 RESEND] cxl/hdm: Allow zero sized HDM decoders ---
> commit 69f9a310ab608be9b469a96819d45389f215c346
> Author: Richard Cheng <[email protected]>
> 
> cxl/hdm: Allow zero sized HDM decoders
> 
> This commit allows the CXL subsystem to accept zero-sized HDM decoders
> instead of rejecting them during port enumeration. It treats empty decoders
> as first-class by backing them with a kmalloc'd resource and keeping the
> skip and hdm_end accounting intact.
> 
> > diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> > --- a/drivers/cxl/core/hdm.c
> > +++ b/drivers/cxl/core/hdm.c
> 
> [ ... ]
> 
> > @@ -545,7 +569,7 @@ int cxl_dpa_free(struct cxl_endpoint_decoder *cxled)
> >  	struct device *dev = &cxled->cxld.dev;
> >  
> >  	guard(rwsem_write)(&cxl_rwsem.dpa);
> > -	if (!cxled->dpa_res)
> > +	if (cxled_empty(cxled))
> 
> [Severity: High]
> Does this early return skip the necessary cleanup for zero-sized decoders?
> 
> When cxled_empty(cxled) evaluates to true for a zero-sized decoder that
> has a valid dpa_res, returning 0 here skips devm_cxl_dpa_release().
> Since the reservation is backed by a kmalloc'd resource from
> cxl_dpa_request_region(), does this leak the dpa_res memory?
> 
> Additionally, skipping devm_cxl_dpa_release() means port->hdm_end is not
> decremented. Because CXL DPA management strictly enforces LIFO teardown,
> will this strand the hdm_end watermark and permanently break the ability
> to free or reconfigure prior decoders on the same port?
> 
> >  		return 0;
> >  	if (cxled->cxld.region) {
> >  		dev_dbg(dev, "decoder assigned to: %s\n",
>

Ignore this one as stated in v6
https://lore.kernel.org/all/akYSpn_EyYTys6Fh@MWDK4CY14F/

--Richard
 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1