linux-kernel - Re: [PATCH] cxl/hdm: allow zero sized committed decoders

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Message-ID: <43ca6827-2bcc-41d3-8a7b-3aec24f2b0e1@intel.com>
Date: Fri, 3 Oct 2025 09:14:28 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Vishal Aslot <vaslot@...dia.com>, Gregory Price <gourry@...rry.net>
Cc: Davidlohr Bueso <dave@...olabs.net>,
 Jonathan Cameron <jonathan.cameron@...wei.com>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>, Li Ming <ming.li@...omail.com>,
 Peter Zijlstra <peterz@...radead.org>,
 Dan Carpenter <dan.carpenter@...aro.org>,
 Zijun Hu <zijun.hu@....qualcomm.com>,
 "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: allow zero sized committed decoders



On 10/2/25 6:03 PM, Vishal Aslot wrote:
>> ________________________________________
>> From: Dave Jiang <dave.jiang@...el.com>
>> Sent: Thursday, October 2, 2025 10:32 AM
>> To: Gregory Price; Vishal Aslot
>> Cc: Davidlohr Bueso; Jonathan Cameron; Alison Schofield; Vishal Verma; Ira Weiny; Dan Williams; Li Ming; Peter Zijlstra; Dan Carpenter; Zijun Hu; linux-cxl@...r.kernel.org; linux-kernel@...r.kernel.org
>> Subject: Re: [PATCH] cxl/hdm: allow zero sized committed decoders
>>
>> External email: Use caution opening links or attachments
>>
>>
>> On 10/1/25 10:48 PM, Gregory Price wrote:
>>> On Wed, Oct 01, 2025 at 08:37:26PM +0000, Vishal Aslot wrote:
>>>> @@ -1210,6 +1210,11 @@ int devm_cxl_enumerate_decoders(struct cxl_hdm *cxlhdm,
>>>>                 rc = init_hdm_decoder(port, cxld, target_map, hdm, i,
>>>>                                       &dpa_base, info);
>>>>                 if (rc) {
>>>> +                       if (rc == -ENOSPC) {
>>>> +                               put_device(&cxld->dev);
>>>> +                               rc = 0;
>>>> +                               continue;
>>>> +                       }
>>>
>>> How do you suggest actually testing this? I briefly poked at this in
>>> QEMU trying to commit decoders, but i found myself incapable of
>>> exercising this path.
> 
> I tested it locally with our BIOS (UEFI) where we commit and lock all decoders and
> all except decoder 0 are zero-sized.
> 
>>
>> It may be worthwhile adding a cxl_test test case for this.
> 
> Yeah, sure. Would cxl mock tests be the right place to explore this?

Yes. Under tools/testing/cxl. Let me know if you need help with that.

DJ

> 
>>>
>>>>                         dev_warn(&port->dev,
>>>>                                  "Failed to initialize decoder%d.%d\n",
>>>>                                  port->id, i);
>>>> --
>>>> 2.34.1
>