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

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Message-ID:
 <SN7PR12MB8131FC2DE9E9A521CE91339DBBE5A@SN7PR12MB8131.namprd12.prod.outlook.com>
Date: Sat, 4 Oct 2025 14:05:03 +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: Friday, October 3, 2025 11:14 AM
> To: Vishal Aslot; Gregory Price
> 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 10/2/25 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

Hi Dave,
    Would the test be a separate patch or part of this one? Thanks.
-Vishal

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