linux-kernel - Re: [PATCH] [EFI,PCI] Allow disabling PCI busmastering on bridges during boot

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Message-ID: <CACdnJuv50s61WPMpHtrF6_=q3sCXD_Tm=30mtLnR_apjV=gjQg@mail.gmail.com>
Date:   Tue, 3 Dec 2019 11:41:32 -0800
From:   Matthew Garrett <mjg59@...gle.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     linux-efi <linux-efi@...r.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        X86 ML <x86@...nel.org>, linux-pci <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [EFI,PCI] Allow disabling PCI busmastering on bridges
 during boot

On Tue, Dec 3, 2019 at 7:30 AM Andy Lutomirski <luto@...capital.net> wrote:

> Would a similar patch apply to non-EFI boot?  That is, in a BIOS boot,
> is busmastering on when the kernel is loaded?

It's only relevant where firmware configures the IOMMU but then
removes that configuration before handing control to the OS. I'm not
aware of that happening anywhere other than EFI.