Re: [kvm-unit-tests PATCH v1 0/7] x86_64 UEFI set up process refactor and scripts fixes

[Zixuan Wang <zxwang42@gmail.com>]

On Sun, Oct 31, 2021 at 9:14 AM Marc Orr <marcorr@google.com> wrote:
>
> On Sun, Oct 31, 2021 at 12:28 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
> >
> > On 31/10/21 06:56, Zixuan Wang wrote:
> > > Hello,
> > >
> > > This patch series refactors the x86_64 UEFI set up process and fixes the
> > > `run-tests.sh` script to run under UEFI. The patches are organized as
> > > three parts.
> > >
> > > The first part (patches 1-2) refactors the x86_64 UEFI set up process.
> > > The previous UEFI setup calls arch-specific setup functions twice and
> > > generates arch-specific data structure. As Andrew suggested [1], we
> > > refactor this process to make only one call to the arch-specific
> > > function and generate arch-neutral data structures. This simplifies the
> > > set up process and makes it easier to develop UEFI support for other
> > > architectures.
> > >
> > > The second part (patch 3) converts several x86 test cases to
> > > Position-Independent Code (PIC) to run under UEFI. This patch is ported
> > > from the initial UEFI support patchset [2] with fixes to the 32-bit
> > > compilation.
> > >
> > > The third part (patches 4-7) fixes the UEFI runner scripts. Patch 4 sets
> > > UEFI OVMF image as readonly. Patch 5 fixes test cases' return code under
> > > UEFI, enabling Patch 6-7 to fix the `run-tests.sh` script under UEFI.
> > >
> > > This patch set is based on the `uefi` branch.
> >
> > Thank you, for patches 1-6 I have squashed the patches when applicable
> > (1, 4, 5, 6) and queued the others (2 and 3).
> >
> > I did not queue patch 7 yet, it seems okay but I want to understand
> > better the changes it needs in the harness and what is missing.  I'll
> > take a look during the week.
>
> SGTM, thank you! Zixuan and I discussed a few things that are missing:
>
> 1. Test cases that take the `-append` arg are currently marked `SKIP`.
> Two issues need to be resolved here. First, we're not using QEMU's
> `-kernel` flag for EFI test cases [1]. And the `-append` flag does not
> work without the `-kernel` flag. I don't understand the details on why
> we don't use the `-kernel` flag myself. Maybe Zixuan can elaborate.
> Second, assuming we fix the first issue, then we need to enlighten the
> KVM-Unit-Tests under UEFI to parse kernel command line arguments and
> pass them down to the test cases via `argv`. Zixuan pointed out to me
> that there is some prior work from Drew [2] that we should be able to
> follow to make this work. So I'm hoping that Zixuan and I can work
> together on solving these issues to get the argument passing working
> next.

Thank you for the detailed summary!

Current kvm-unit-tests pass an EFI binary as part of a disk image,
instead of using the `-kernel` argument.

I just tested the `-kernel` argument and it seems to work with EFI
binaries, and more importantly, it's really fast (bypassing the
default 5-second user input waiting). I will update the `x86/efi/run`
to use `-kernel` argument to pass the EFI binaries.

Since `-kernel` is working, I can start to investigate how to use
`-append` to pass arguments. If that doesn't work well, an alternative
approach could be:

1. (host) create a file `args.txt` in the disk image, which contains
all the arguments needed
2. (guest) call UEFI filesystem interface to read this `args.txt` from
the disk image, parse it and pass the arguments to `main()`

> 2. We need a way to annotate test cases in `x86/unittests.cfg` as
> known to work under SEV. I'm thinking of doing this via new (very
> broad) test groups in `unittests.cfg`. I _think_ SEV is the primary
> scenario we care about. However, folks may care about running the test
> cases under UEFI outside of SEV. For example, last time I checked,
> emulator runs OK under UEFI minus SEV-ES but fails under SEV-ES. And
> similarly, while most test cases work under UEFI minus SEV, there are
> a few that do mis-behave -- and it probably makes sense to document
> this (e.g., via annotations in `unittests.cfg`). Also, there are many
> variations of SEV (SEV, SEV-ES, SEV-SNP)... And hopefully some of this
> will eventually be applicable to TDX as well. So many testgroups is
> not a good solution. I'm not sure.

Adding an `efi` group seems helpful. E.g., the current `x86/smap.c`
does not work under UEFI; but the `run-tests.sh` still tries to run
this test case, even if this test case is not compiled.

> 3. Multi-CPU needs to be made to work under UEFI. For now, patch #7
> forces all EFI test cases to run with 1 vCPU. I chatted with Brijesh,
> and he mentioned that Varad would like to work on this. However, if
> anything here changes, please let me know, because we can work on this
> as well. But for now, I'm not planning to work on it so we can avoid
> duplicating work.
> 4. UEFI runs a lot slower than SEABIOS. It doesn't help that the test
> harness launches QEMU more than once for each test case (i.e., it runs
> the `_NO_FILE_4Uhere_` scenario to check QEMU arguments). I'm not sure
> how much of an issue this is in practice. Depending on the answer, I
> know Zixuan had some ideas on how to speed this up in the current test
> harness. Or maybe we can explore an alternative to the
> `_NO_FILE_4Uhere_` approach instead.

As the `-kernel` argument now works with the EFI binaries and is
significantly faster, this should not be an issue anymore. We just
need to update the runner scripts to use `-kernel` argument.

> Zixuan: Please add/correct anything as needed!
>
> [1] https://gitlab.com/kvm-unit-tests/kvm-unit-tests/-/blob/uefi/x86/run#L42-44
> [2] https://github.com/rhdrjones/kvm-unit-tests/blob/target-efi/scripts/mkefi.sh
>
> Thanks,
> Marc

Best regards,
Zixuan