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

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Message-ID: <CAMj1kXFvMVmxesoqaW254z85ZMRO4U+S3Cr7oyu4K-m-jiKVTg@mail.gmail.com>
Date: Thu, 10 Jul 2025 09:14:30 +1000
From: Ard Biesheuvel <ardb@...nel.org>
To: Krzysztof Kozlowski <krzk@...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 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.