[kata-dev] Booting OVMF with -bios?

Christophe de Dinechin dinechin at redhat.com
Wed Jan 6 17:35:09 UTC 2021

> On 6 Jan 2021, at 18:07, Laszlo Ersek <lersek at redhat.com> wrote:
> Hi Christophe!
> On 01/06/21 16:11, Christophe de Dinechin wrote:
>> Hello Laszlo,
>> Happy New Year!
> Same to you :)
>> I may need to pick your brain a little regarding an issue someone testing
>> AMD SEV ran into with Kata.
>> Basically, here are the questions I have:
>> 1) Is it OK to pass an OVMF firmware to the -boot option of qemu?
>>   What about SecureBoot in that case?
>> 2) Are there any expected behavioral differences between booting with the
>>   -bios option and using a -drive if=pflash option? In particular, anything
>>   that could prevent SEV from activating in the guest kernel?
>> 3) Knowing that in the Kata case, we don't care about anything persisting
>>   across reboots, is there any problem passing only the OVMF_CODE.fd image
>>   readonly using the -drive option, without having an OVMF_VARS.fd? Asking
>>   to see if we need to create an OVMF_VARS.fd for each container.
>> If you need a bit of context:
>> https://github.com/kata-containers/kata-containers/issues/1231 and
>> http://lists.katacontainers.io/pipermail/kata-dev/2021-January/001638.html
> "-bios" should never be used with OVMF. If you don't need non-volatile
> UEFI variables to persist from one boot of the domain to the next,
> that's fine; in that case, please use a throw-away regular file for the
> variable store pflash chip. this file should be instantiated from
> "OVMF_VARS.fd", if you don't want the Secure Boot operational mode
> enabled right off the bat; otherwise, please copy (create) the domain's
> varstore from "OVMF_VARS.secboot.fd", before launching QEMU.

OK. Need to figure out how we package that image for Kata.

> We have never tested SEV with "-bios" (well, because "-bios" is wrong to
> use with OVMF in the first place, regardless of SEV); and yes there have
> been SEV-related changes, specific to the flash driver in OVMF. (QEMU
> too received SEV-related changes around the parts responsible for
> loading OVMF, in "hw/i386/pc_sysfw.c".)

If that's not supposed to work, is there some relatively simple way to warn?
Right now, while all the doc I saw about 

> The particulars of a SEV failure, when using "-bios", aren't even worth
> investigating -- please try to reproduce the issue first with two pflash
> chips.

Actually, I'm more interested in the correct way to fix it for Kata.

So I gather that the right approach is
- Create a copy of the right OVMF_VARS file
- Change the command line to have the correct two -drive options

Will do that.

Thanks a lot,
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