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

[Stefan Hajnoczi <stefanha@redhat.com>]

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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
> 
> diff --git a/meson.build b/meson.build
> index 20ceeb8158..8a17c29de8 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -960,6 +960,13 @@ if not get_option('slirp').auto() or have_system
>    endif
>  endif
>  
> +sev = not_found
> +if not get_option('sev').auto()

When 'sev' is auto, then it won't be built. That seems strange. The
auto-detection part is missing! I did you test this on a system that
doesn't have libsev installed system-wide?

I guess the auto-detection would look something like:

  cargo = find_program('cargo', required: true)

  if not get_option('sev').auto() or cargo.found()
      ...

That way 'sev' is only built automatically on systems that have cargo
installed.

> +  sev = dependency('sev',
> +                   method: 'pkg-config',
> +                   required: get_option('sev'))
> +endif

If you update the auto logic, see the documentation about fallbacks to
subprojects for optional dependencies:
https://mesonbuild.com/Wrap-dependency-system-manual.html#provide-section

It might be necessary to add dependency(..., fallback='sev').

> +
>  vde = not_found
>  if not get_option('vde').auto() or have_system or have_tools
>    vde = cc.find_library('vdeplug', has_headers: ['libvdeplug.h'],
> @@ -4331,6 +4338,7 @@ summary_info += {'libudev':           libudev}
>  # Dummy dependency, keep .found()
>  summary_info += {'FUSE lseek':        fuse_lseek.found()}
>  summary_info += {'selinux':           selinux}
> +summary_info += {'sev':               sev}
>  summary_info += {'libdw':             libdw}
>  summary(summary_info, bool_yn: true, section: 'Dependencies')
>  
> diff --git a/meson_options.txt b/meson_options.txt
> index 57e265c871..5b8d283717 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -204,6 +204,8 @@ option('sdl_image', type : 'feature', value : 'auto',
>         description: 'SDL Image support for icons')
>  option('seccomp', type : 'feature', value : 'auto',
>         description: 'seccomp support')
> +option('sev', type : 'feature', value : 'auto',
> +        description: 'Rust AMD SEV library')
>  option('smartcard', type : 'feature', value : 'auto',
>         description: 'CA smartcard emulation support')
>  option('snappy', type : 'feature', value : 'auto',
> diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
> index e4b46d5715..e585a548fa 100644
> --- a/scripts/meson-buildoptions.sh
> +++ b/scripts/meson-buildoptions.sh
> @@ -161,6 +161,7 @@ meson_options_help() {
>    printf "%s\n" '  sdl-image       SDL Image support for icons'
>    printf "%s\n" '  seccomp         seccomp support'
>    printf "%s\n" '  selinux         SELinux support in qemu-nbd'
> +  printf "%s\n" '  sev             SEV library support'
>    printf "%s\n" '  slirp           libslirp user mode network backend support'
>    printf "%s\n" '  slirp-smbd      use smbd (at path --smbd=*) in slirp networking'
>    printf "%s\n" '  smartcard       CA smartcard emulation support'
> @@ -440,6 +441,8 @@ _meson_option_parse() {
>      --disable-seccomp) printf "%s" -Dseccomp=disabled ;;
>      --enable-selinux) printf "%s" -Dselinux=enabled ;;
>      --disable-selinux) printf "%s" -Dselinux=disabled ;;
> +    --enable-sev) printf "%s" -Dsev=enabled ;;
> +    --disable-sev) printf "%s" -Dsev=disabled ;;
>      --enable-slirp) printf "%s" -Dslirp=enabled ;;
>      --disable-slirp) printf "%s" -Dslirp=disabled ;;
>      --enable-slirp-smbd) printf "%s" -Dslirp_smbd=enabled ;;
> diff --git a/subprojects/sev.wrap b/subprojects/sev.wrap
> new file mode 100644
> index 0000000000..5be1faccf6
> --- /dev/null
> +++ b/subprojects/sev.wrap
> @@ -0,0 +1,6 @@
> +[wrap-git]
> +url = https://github.com/tylerfanelli/sev
> +revision = b81b1da5df50055600a5b0349b0c4afda677cccb
> +
> +[provide]
> +sev = sev_dep
> diff --git a/target/i386/meson.build b/target/i386/meson.build
> index 6f1036d469..8972a4fb17 100644
> --- a/target/i386/meson.build
> +++ b/target/i386/meson.build
> @@ -20,7 +20,7 @@ i386_system_ss.add(files(
>    'monitor.c',
>    'cpu-sysemu.c',
>  ))
> -i386_system_ss.add(when: 'CONFIG_SEV', if_true: files('sev.c'), if_false: files('sev-sysemu-stub.c'))
> +i386_system_ss.add(when: 'CONFIG_SEV', if_true: [sev, files('sev.c')], if_false: files('sev-sysemu-stub.c'))
>  
>  i386_user_ss = ss.source_set()
>  
> -- 
> 2.40.1
> 

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