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

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Message-ID: <8877e886-c7f4-42c0-8e1d-422a40d6e092@intel.com>
Date: Mon, 6 Oct 2025 07:54:07 -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 10/4/25 7:05 AM, Vishal Aslot wrote:
>> ________________________________________
>> 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.

It would be a separate patch and you post a series with a cover letter. You can see examples in the lore archive [1] of submissions more than 1 patches.

[1]: https://lore.kernel.org/linux-cxl/

DJ

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