linux-kernel - Re: [PATCH v3 0/2] efi/x86: Call set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <pqPZcYgBsBnpSd8MTxyDtnXAeWgjlIhAgUK_nGg-s4IbXPl311zGwY6saehL0ODtShMvUpTEo-K6PlJw5DivrdeHolVNUVM5MJii0K4Lq48=@proton.me>
Date: Wed, 17 Jul 2024 18:27:17 +0000
From: Sharpened Blade <sharpenedblade@...ton.me>
To: Aditya Garg <gargaditya08@...e.com>
Cc: Ard Biesheuvel <ardb@...nel.org>, "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Hans de Goede <hdegoede@...hat.com>, Lukas Wunner <lukas@...ner.de>, Kerem Karabay <kekrby@...il.com>, Orlando Chamberlain <orlandoch.dev@...il.com>
Subject: Re: [PATCH v3 0/2] efi/x86: Call set_os() protocol on dual GPU Macs

> Hi Ard
> 
> > Hi,
> > 
> > Is this a theoretical concern? Or are you aware of any user that is
> > actually affected by this?
> 
> 
> We had a Mac Mini user who wasn't able to use hybrid graphics
> on his Mac after using the eGPU. So no, it's not a theoretical concern
> 
> > In any case, given the niche nature, enabling this more widely by
> > default does not seem like a great approach, as the risk for
> > regressions outweighs the benefit.
> > 
> > I could imagine the use of a EFI variable to opt into this, would that
> > work? It would have to be set only once from user space (using
> > efivarfs)
> 
> 
> I'm not really sure about efivars here, but am ready to test. As long as
> it doesn't break booting of macOS or Windows, I don't find it an issue.
> macOS may also reset the variable, again have to verify by testing the same.

On my mac, macOS does not reset EFI variables that it does not use. It should be the same for other models and firmware versions.

> I guess it will also get reset if a users resets their NVRAM.

Users have to manually reset their nvram so this will not happen during normal usage. This is actually a good thing since users can easily disable the eGPU if it is misbehaving and they dont have graphical output.