On 21/03/2022 21:47, Palmer Dabbelt wrote:
On Sun, 20 Mar 2022 22:43:07 PDT (-0700), alistai...@gmail.com wrote:
On Thu, Mar 17, 2022 at 7:46 PM Peter Maydell
<peter.mayd...@linaro.org> wrote:
On Wed, 16 Mar 2022 at 22:23, Alistair Francis <alistai...@gmail.com>
wrote:
> Hmm... This seems like a bug. We shouldn't allow the user to specify a
> `-bios` option if using KVM. Would you mind preparing a patch to catch
> this?
You don't want to allow the possibility of a bios blob that expects
to run in S-mode, the way arm virt can run an EL1 UEFI BIOS ?
Interesting. We could still allow that by using -device loader though.
If we load something in S mode it really is a kernel and not firmware,
so I think the -bios argument is a little misleading. We could make
-bios and -enable-kvm a warning instead, to discourage users from
providing OpenSBI, but still allow them to pass something.
We could handle this in OpenSBI: have it just detect that it's been
launched in S-mode and just jump to the payload.
To me not allowing it seems reasonable, and we can always re-allow it
in the future if there is a good use case.
That also seems fine to me. There'd be a lot of work involved in doing
anything useful with S-mode firmware, given that things aren't really
designed to work that way. Certainly a lot more work than re-enabling
this sort of flag, and while it might be a bit of a headache coupling
that to a QEMU source-level change my guess is that there'd need to be a
bunch of work done on new HW interfaces to make this useful so there'd
be QEMU changes to emulate those either way.
Having at least a warning seems prudent, as most users are going to end
up with a hang here and a silent hang is a headache for everyone.
Okay, my analysis was wrong, -bios is in fact already ignored when being
used in combination with -enable-kvm on the virt machine model. See:
https://git.qemu.org/?p=qemu.git;a=blob;f=hw/riscv/virt.c;h=da50cbed43ec54777992d40dbf158ec63fccef03;hb=HEAD#l1314
However, the bios will be silently ignored and dropped, which led me to
the mistake. I'll provide a patch that gives a warning to the user.
Ralf
Alistair
thanks
-- PMM
