Re: [RFC PATCH v2 1/9] Add Rust SEV library as subproject

[Philippe Mathieu-Daudé]

On 5/3/24 14:47, Daniel P. Berrangé wrote:
> On Wed, Oct 04, 2023 at 04:34:10PM -0400, Tyler Fanelli wrote:
> > The Rust sev library provides a C API for the AMD SEV launch ioctls, as
> > well as the ability to build with meson. Add the Rust sev library as a
> > QEMU subproject with the goal of outsourcing all SEV launch ioctls to C
> > APIs provided by it.
> >
> > Signed-off-by: Tyler Fanelli <tfanelli@redhat.com>
> > ---
> >   meson.build                   | 8 ++++++++
> >   meson_options.txt             | 2 ++
> >   scripts/meson-buildoptions.sh | 3 +++
> >   subprojects/sev.wrap          | 6 ++++++
> >   target/i386/meson.build       | 2 +-
> >   5 files changed, 20 insertions(+), 1 deletion(-)
> >   create mode 100644 subprojects/sev.wrap


> Now, the second issue is that my patch to QEMU's meson.build where
> I look for "CONFIG_SEV" is wrong. I've not tested whether it behaves
> correctly on non-x86 hosts - basically I'm hoping that CONFIG_SEV is
> *NOT* present if building qemu-system-x86_64 on an aarch64 host.

See hw/i386/Kconfig:

  config SEV
      bool
      ...
      depends on KVM

and meson.build ($cpu is the host):

  ...
elif cpu == 'x86'
  host_arch = 'i386'

if cpu in ['x86', 'x86_64']
  kvm_targets = ['i386-softmmu', 'x86_64-softmmu']

So SEV is only on selectable on x86 hosts, with KVM enabled.

> Assuming we get this logic correct though, this unblocks one issue
> with getting this merged - Rust platform support.
>
> We've said we want Rust platform support to be a match for QEMU's
> platform support. We're probably pretty close, but still it is a
> review stumbling block.
>
> If, however, we demonstrate that we /only/ try to use libsev crate
> when building on an x86_64 host, then we don't need to think about
> Rust platform support in any detail. We know Rust is fully supported
> on x86_64 on Linux, and we're not introducing any Rust dependency
> for QEMU on other build target arches.
>
> With regards,
> Daniel