tboot UEFI and Xen (was Re: i915 dma faults on Xen)

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Thu, Oct 15, 2020 at 1:13 PM Jason Andryuk <jandryuk@xxxxxxxxx> wrote:
>
> On Thu, Oct 15, 2020 at 12:39 PM Tamas K Lengyel
> <tamas.k.lengyel@xxxxxxxxx> wrote:
> >
> > > > Can you paste the memory map as printed by Xen when booting, and what
> > > > command line are you using to boot Xen.
> > >
> > > So this is OpenXT, and it's booting EFI -> xen -> tboot -> xen
> >
> > Unrelated comment: since tboot now has a PE build
> > (http://hg.code.sf.net/p/tboot/code/rev/5c68f0963a78) I think it would
> > be time for OpenXT to drop the weird efi->xen->tboot->xen flow and
> > just do efi->tboot->xen. Only reason we did efi->xen->tboot was
> > because tboot didn't have a PE build at the time. It's a very hackish
> > solution that's no longer needed.
>
> Thanks for the pointer, Tamas.  If I recall correctly, there was also
> an issue with ExitBootServices.  Do you know if that has been
> addressed?

I tested tboot's UEFI build, but it didn't boot Xen:

Fedora UEFI shim -> grub2 -> tboot.mb2 -> xen
didn't work - hung at a black screen. Power button powered off
promptly, so it didn't get far enough for something to enable ACPI.
Fedora UEFI shim -> grub2 -> tboot.mb2 -> linux
booted and showed efi stuff in /sys

Naturally this is on a laptop without a serial port. I haven't looked
into this further as it's a low priority for me at this time.

Regards,
Jason