Re: [Xen-devel] [PATCH] tools: probe for existence of qemu-xen trace backends.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 10 Feb 2016, Ian Campbell wrote:
> QEMU upstream commit ed7f5f1d8db0 ("trace: convert stderr backend to
> log") renamed the stderr trace backend to log, which breaks the xen
> build when pointed at a QEMU tree after that point:
> 
> ./configure of QEMU fail with:
> "ERROR: invalid trace backends
>         Please choose supported trace backends."
> 
> These changes are not (yet) present in qemu-xen-unstable.git and in
> any case we want to support QEMU before and after this change. Use the
> tracetool.py provided by QEMU to probe for supported trace backends.
> 
> This is now done unconditionally (not depending on debug=y), which is
> simpler to arrange here but also follows upstream QEMU which in
> baf86d6b3ca0 ("trace: switch default backend to "log"") switched the
> default from "nop" to "log", so we would have got log in debug=no
> builds from then on anyway.
> 
> Tested with current qemu-xen-unstable (f165e581d9a6) and current QEMU
> upstream master (f075c89f0a9c), the latter picked up via:
>     QEMU_UPSTREAM_URL := /path/to/qemu-xen.git
> which therefore tested the out of tree build aspect of this change.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> ---
>  tools/Makefile | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/Makefile b/tools/Makefile
> index 5688a7c..76a2235 100644
> --- a/tools/Makefile
> +++ b/tools/Makefile
> @@ -228,7 +228,7 @@ qemu-xen-dir-force-update: qemu-xen-dir-find
>       fi
>  
>  ifeq ($(debug),y)
> -QEMU_XEN_ENABLE_DEBUG := --enable-debug --enable-trace-backend=stderr
> +QEMU_XEN_ENABLE_DEBUG := --enable-debug
>  else
>  QEMU_XEN_ENABLE_DEBUG :=
>  endif
> @@ -240,8 +240,16 @@ subdir-all-qemu-xen-dir: qemu-xen-dir-find
>               source=.; \
>       fi; \
>       cd qemu-xen-dir; \
> +     if $$source/scripts/tracetool.py --check-backends --backends log ; then 
> \

--check-backends only works on qemu-xen >= 4.6, on the other hand we
know that qemu-xen < 4.6 supports stderr.

Maybe:

if $$source/scripts/tracetool.py --check-backends --backends log &>/dev/null
then
    enable_trace_backend='--enable-trace-backend=log'
else
    enable_trace_backend='--enable-trace-backend=stderr'
fi

?


> +             enable_trace_backend='--enable-trace-backend=log'; \
> +     elif $$source/scripts/tracetool.py --check-backends --backends stderr ; 
> then \
> +             enable_trace_backend='--enable-trace-backend=stderr'; \
> +     else \
> +             enable_trace_backend='' ; \
> +     fi ; \
>       $$source/configure --enable-xen --target-list=i386-softmmu \
>               $(QEMU_XEN_ENABLE_DEBUG) \
> +             $$enable_trace_backend \
>               --prefix=$(LIBEXEC) \
>               --libdir=$(LIBEXEC_LIB) \
>               --includedir=$(LIBEXEC_INC) \
> -- 
> 2.1.4
> 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel