From: Stefan Fritsch Subject: Re: AMD SEV: confidential autoconf whitelist To: Theo de Raadt Cc: Mark Kettenis , Hans-Jörg Höxer , tech@openbsd.org Date: Tue, 9 Sep 2025 21:19:18 +0200 On Tue, 9 Sep 2025, Theo de Raadt wrote: > Stefan Fritsch wrote: > > > > > struct cfdriver acpi_cd = { > > > > - NULL, "acpi", DV_DULL > > > > + NULL, "acpi", DV_DULL, CD_COCOVM > > > > }; > > > > > > I still think that by including acpi(4) in the list of allowed drivers > > > you have included the driver with the largest possible attack surface. > > > And our the AML interpreter code certainly isn't the best quality code > > > in our tree. > > > > Making ACPI secure will be some big piece of work in the future. For not > > it is neccessary. > > I don't see how that can ever be achieved, because it is a turing-complete > engine. > > I'll go back to my suggestion to try to use MPBIOS information if it exists. I agree that making ACPI secure means not parsing any AML. So maybe it will involve finding other sources for the information we need from the DSDT/SSDT. Maybe in the end it will allow us to simply disable acpi(4). SEV-SNP already defines a way to get the APIC IDs of all present CPUs. Knowledge about IO APICs could be replaced by using MSI/MSI-X exclusively or by using some para-virtualized intterupt controller. We will have to see what other pieces we absolutely need. PCI busses come to mind.