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

[Matthew Garrett]

On Wed, Dec 4, 2019 at 11:50 AM Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> Wouldn't it also be applicable in the much simpler case where the
> firmware hands over control with no IOMMU configured but also with the
> busmastering bit cleared.  Does firmware do this?  Does the kernel
> currently configure the iOMMU before enabling busmastering?

We already handle this case - the kernel doesn't activate busmastering
until after it does IOMMU setup.