Re: [PATCH v4 4/4] PCI/ACS: Enable PCI_ACS_TB for untrusted/external-facing devices

[Joerg Roedel]

On Sat, Jul 11, 2020 at 09:58:38PM -0500, Bjorn Helgaas wrote:
> If BIOS handed off with ATS enabled and we somehow relied on it being
> already enabled, something might break if we start disabling ATS.
> Just a theoretical possibility, doesn't seem likely to me.

I don't think this will be a problem. When the BIOS enables ATS for a
device it also needs to enable the IOMMU already, an we are not handling
an already enabled IOMMU (outside of kdump kernels) very well.


Regards,

	Joerg