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

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Message-ID:
 <SN7PR12MB8131EE31375531673BCF0C62BBE4A@SN7PR12MB8131.namprd12.prod.outlook.com>
Date: Fri, 3 Oct 2025 01:03:16 +0000
From: Vishal Aslot <vaslot@...dia.com>
To: Dave Jiang <dave.jiang@...el.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

> ________________________________________
> 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?

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