linux-kernel - Re: [PATCH v2] efi: add ovmf debug log driver

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Message-ID: <d2b283f9-18bf-4fc9-b888-997dbe9d9390@kernel.org>
Date: Thu, 10 Jul 2025 08:41:34 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Gerd Hoffmann <kraxel@...hat.com>, linux-efi@...r.kernel.org,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] efi: add ovmf debug log driver

On 10/07/2025 01:14, Ard Biesheuvel wrote:
> On Thu, 10 Jul 2025 at 00:39, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>
>> On 09/07/2025 16:31, Gerd Hoffmann wrote:
>>> On Wed, Jul 09, 2025 at 04:20:49PM +0200, Krzysztof Kozlowski wrote:
>>>> On 09/07/2025 16:17, Gerd Hoffmann wrote:
>>>>> On Wed, Jul 09, 2025 at 03:58:58PM +0200, Krzysztof Kozlowski wrote:
>>>>>> On 08/07/2025 14:56, Gerd Hoffmann wrote:
>>>>>>> +MODULE_DESCRIPTION("OVMF debug log");
>>>>>>> +MODULE_AUTHOR("Gerd Hoffmann <kraxel@...hat.com>");
>>>>>>> +MODULE_LICENSE("GPL");
>>>>>>> +MODULE_ALIAS("platform:ovmf_debug_log");
>>>>>>> diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
>>>>>>> index db8c5c03d3a2..ac0a03ec3452 100644
>>>>>>> --- a/drivers/firmware/efi/Kconfig
>>>>>>> +++ b/drivers/firmware/efi/Kconfig
>>>>>>> @@ -263,6 +263,14 @@ config EFI_COCO_SECRET
>>>>>>>     virt/coco/efi_secret module to access the secrets, which in turn
>>>>>>>     allows userspace programs to access the injected secrets.
>>>>>>>
>>>>>>> +config OVMF_DEBUG_LOG
>>>>>>> + tristate "Expose OVMF firmware debug log via sysfs"
>>>>>>> + depends on EFI
>>>>>>> + help
>>>>>>> +   Recent OVMF versions (edk2-stable202508 + newer) can write
>>>>>>> +   their debug log to a memory buffer.  This driver exposes the
>>>>>>> +   log content via sysfs (/sys/firmware/efi/ovmf_debug_log).
>>>>>>
>>>>>> Where did you document new ABI?
>>>>>
>>>>> The log buffer header struct is documented in the header file for the
>>>>> edk2 code:
>>>>> https://github.com/tianocore/edk2/blob/master/OvmfPkg/Include/Library/MemDebugLogLib.h
>>>>
>>>> You added a new sysfs interface. I meant documentation for this.
>>>
>>> The sysfs file contains the log and you can simply use
>>> 'cat /sys/firmware/efi/ovmf_debug_log' to read it.
>>
>> Don't explain how it works to me. I did not ask how it works. I asked
>> where is the new ABI documented?
>>
> 
> Please drop the condescending tone, and don't make people guess at
> what you are trying to say.
> 
> If you meant to say that the patch lacks an ABI description in
> Documentation/ABI, then you are absolutely right, and you can just say
> so.

Maybe it was documented already, so I asked where ABI is documented. I
think this was exactly what you said here - Documentation/ABI:

"Where did you document new ABI?"

Best regards,
Krzysztof