Re: [PATCH] tracing: deprecate "ust" tracing backend

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

On Fri, Sep 19, 2025 at 12:10:21PM +0200, Paolo Bonzini wrote:
> The "ust" backend is complex (tracetool contains two output formats just
> for that backend).  It is not clear if if it has any users, and LTTng
> anyway can use the uprobe tracepoints provided by the "dtrace" backend,
> therefore deprecate "ust".
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  docs/about/deprecated.rst | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
> index aa300bbd507..57250f9d47f 100644
> --- a/docs/about/deprecated.rst
> +++ b/docs/about/deprecated.rst
> @@ -533,3 +533,12 @@ command documentation for details on the ``fdset`` usage.
>  
>  The ``zero-blocks`` capability was part of the block migration which
>  doesn't exist anymore since it was removed in QEMU v9.1.
> +
> +Host features
> +-------------
> +
> +``ust`` tracing backend
> +-----------------------
> +
> +LTTng can use uprobe tracepoints, therefore it is recommended to use
> +the ``dtrace`` backend instead.

meson.build should call

   warning('ust trace backend is deprecated, use dtrace backend for uprobe support')


if the user requests ust at build time.

With regards,
Daniel
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