netdev - Re: [PATCH v17 00/22] Type2 device basic support

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Message-ID: <e74a66db-6067-4f8d-9fb1-fe4f80357899@amd.com>
Date: Thu, 28 Aug 2025 09:02:11 +0100
From: Alejandro Lucero Palau <alucerop@....com>
To: PJ Waskiewicz <ppwaskie@...nel.org>, alejandro.lucero-palau@....com,
 linux-cxl@...r.kernel.org, netdev@...r.kernel.org, dan.j.williams@...el.com,
 edward.cree@....com, davem@...emloft.net, kuba@...nel.org,
 pabeni@...hat.com, edumazet@...gle.com, dave.jiang@...el.com
Subject: Re: [PATCH v17 00/22] Type2 device basic support

Hi PJ,

On 8/27/25 17:48, PJ Waskiewicz wrote:
> On Tue, 2025-06-24 at 15:13 +0100, alejandro.lucero-palau@....com
> wrote:
>
> Hi Alejandro,
>
>> From: Alejandro Lucero <alucerop@....com>
>>
>> v17 changes: (Dan Williams review)
>>   - use devm for cxl_dev_state allocation
>>   - using current cxl struct for checking capability registers found
>> by
>>     the driver.
>>   - simplify dpa initialization without a mailbox not supporting pmem
>>   - add cxl_acquire_endpoint for protection during initialization
>>   - add callback/action to cxl_create_region for a driver notified
>> about cxl
>>     core kernel modules removal.
>>   - add sfc function to disable CXL-based PIO buffers if such a
>> callback
>>     is invoked.
>>   - Always manage a Type2 created region as private not allowing DAX.
>>
> I've been following the patches here since your initial RFC.  What
> platform are you testing these on out of curiosity?


Most of the work was done with qemu. Nowadays, I have several system 
with CXL support and Type2 BIOS support, so it has been successfully 
tested there as well.


> I've tried pulling the v16 patches into my test environment, and on CXL
> 2.0 hosts that I have access to, the patches did not work when trying
> to hook up a Type 2 device.  Most of it centered around many of the CXL
> host registers you try poking not existing.


Can you share the system logs and maybe run it with CXL debugging on?


> I do have CXL-capable BIOS
> firmware on these hosts, but I'm questioning that either there's still
> missing firmware, or the patches are trying to touch something that
> doesn't exist.


May I ask which system are you using? ARM/Intel/AMD/surpriseme? lspci 
-vvv output would also be useful. I did find some issues with how the 
BIOS we got is doing things, something I will share and work on if that 
turns out to be a valid case and not a BIOS problem.


>
> I'm working on rebasing to the v17 patches to see if this resolves what
> I'm seeing.  But it's a bit of a lift, so I figured I'd ask what you're
> testing on before burning more time.
>
> Eventually I'd like to either give a Tested-by or shoot back some
> amended patches based on testing.  But I've not been able to get that
> far yet...


That would be really good. Let's see if we can figure out what is the 
problem there.


Thank you


> Cheers,
> -PJ