Re: [PATCH 02/10] meson: update unsupported host/CPU messages

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Aug 29, 2023 at 10:29:23AM +0200, Paolo Bonzini wrote:
> Unsupported CPU and OSes are not really going away, but the
> project simply does not guarantee that they work.  Rephrase
> the messages accordingly.  While at it, move the warning for
> TCI performance at the end where it is more visible.

I think I agree wrt to CPUs, but in the case of OS I think
it is fairly accurate as-is.

When we bump the minimum version of libraries we will not
pay attention to unsupported OS, so it is entirely possible
to bump to a version that means the ability to run on an
OS goes away entirely (unless the user is willing to rebuild
packages at newer versions).

When writing #ifdefs for portability we also may explicitly
delete #ifdefs from unsupported OS platforms  if we consider
them obsolete enough. So again I think the ability to use an
unsupported OS may indeed goaway entirely.

> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  meson.build | 38 +++++++++++++++++++++-----------------
>  1 file changed, 21 insertions(+), 17 deletions(-)
> 
> diff --git a/meson.build b/meson.build
> index 98e68ef0b1e..02b035a3808 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -678,9 +678,7 @@ endif
>  tcg_arch = host_arch
>  if get_option('tcg').allowed()
>    if host_arch == 'unknown'
> -    if get_option('tcg_interpreter')
> -      warning('Unsupported CPU @0@, will use TCG with TCI (slow)'.format(cpu))
> -    else
> +    if not get_option('tcg_interpreter')
>        error('Unsupported CPU @0@, try --enable-tcg-interpreter'.format(cpu))
>      endif
>    elif get_option('tcg_interpreter')
> @@ -4317,28 +4315,34 @@ summary_info += {'selinux':           selinux}
>  summary_info += {'libdw':             libdw}
>  summary(summary_info, bool_yn: true, section: 'Dependencies')
>  
> -if not supported_cpus.contains(cpu)
> +if host_arch == 'unknown'
>    message()
> -  warning('SUPPORT FOR THIS HOST CPU WILL GO AWAY IN FUTURE RELEASES!')
> +  warning('UNSUPPORTED HOST CPU')
>    message()
> -  message('CPU host architecture ' + cpu + ' support is not currently maintained.')
> -  message('The QEMU project intends to remove support for this host CPU in')
> -  message('a future release if nobody volunteers to maintain it and to')
> -  message('provide a build host for our continuous integration setup.')
> -  message('configure has succeeded and you can continue to build, but')
> -  message('if you care about QEMU on this platform you should contact')
> -  message('us upstream at qemu-devel@nongnu.org.')
> +  message('Support for CPU host architecture ' + cpu + ' is not currently')
> +  message('maintained. The QEMU project does not guarantee that QEMU will')
> +  message('compile or work on this host CPU. You can help by volunteering')
> +  message('to maintain it and providing a build host for our continuous.')
> +  message('integration setup.')
>  endif
>  
>  if not supported_oses.contains(targetos)
>    message()
> -  warning('WARNING: SUPPORT FOR THIS HOST OS WILL GO AWAY IN FUTURE RELEASES!')
> +  warning('UNSUPPORTED HOST OS')
> +  message()
> +  message('Support for host OS ' + targetos + 'is not currently maintained.')
> +  message('The QEMU project does not guarantee that QEMU will compile or')
> +  message('work on this operating system. You can help by volunteering')
> +  message('to maintain it and providing a build host for our continuous.')
> +  message('integration setup.')
> +endif
> +
> +if host_arch == 'unknown' or not supported_oses.contains(targetos)
>    message()
> -  message('Host OS ' + targetos + 'support is not currently maintained.')
> -  message('The QEMU project intends to remove support for this host OS in')
> -  message('a future release if nobody volunteers to maintain it and to')
> -  message('provide a build host for our continuous integration setup.')
>    message('configure has succeeded and you can continue to build, but')
> +  if host_arch == 'unknown' and get_option('tcg').allowed() and target_dirs.length() > 0
> +    message('QEMU will use a slow interpreter to emulate the target CPU;')
> +  endif
>    message('if you care about QEMU on this platform you should contact')
>    message('us upstream at qemu-devel@nongnu.org.')
>  endif
> -- 
> 2.41.0
> 
> 

With regards,
Daniel
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