Yes, I am using OVMF with SEV-ES (sev-es-v12 patches applied). I am
running Ubuntu 18.04 distro. My grub target is x86_64-efi. I also
tried installing the grub-efi-amd64 package. In all cases, the grub is
running in 64bit but enters the startup_32 in 32 bit mode. I think
there should be a 32bit #VC handler just something very similar in the
OVMF patches to handle the cpuid when the CPU is still in 32bit mode.
As it is now, it will be a huge problem to support different distro images.
I wonder if I am the only one having this problem.

-Erdem

On Tue, Jul 21, 2020 at 5:50 AM Joerg Roedel [off-list ref] wrote:

Hi,

On Mon, Jul 20, 2020 at 06:09:19PM -0700, Erdem Aktas wrote:

quoted

It looks like there is an expectation that the bootloader will start
from the 64bit entry point in header_64.S. With the current patch
series, it will not boot up if the bootloader jumps to the startup_32
entry, which might break some default distro images.
What are supported bootloaders and configurations?
I am using grub ( 2.02-2ubuntu8.15) and it fails to boot because of
this reason. I am not a grub expert, so I would appreciate any
pointers on this.

This is right, the only supported boot path is via the 64bit EFI entry
point. The reason is that SEV-ES requires support in the firmware too,
and currently only OVMF is supported in that regard. The firmware needs
to setup the AP jump-table, for example.

Other boot-paths have not been implemented. Booting via startup_32 would
require exception handling in the 32bit-part of the boot-strap code,
because verify_cpu is called there. Also an AMD specific MSR can't be
accessed there because this would #GP on non-AMD/SEV-ES machines and,
as I said, there is no way yet to handle them.

How did you get into the startup_32 entry-point, do you have an SEV-ES
BIOS supporting this? If it is really needed it could be implemented at
a later point.

Regards,

        Joerg