Re: [PATCH] configure: define CONFIG_XEN when Xen is enabled

[Peter Maydell <peter.maydell@xxxxxxxxxx>]

On Tue, 28 Jul 2020 at 10:19, Paul Durrant <paul@xxxxxxx> wrote:
>
> From: Paul Durrant <pdurrant@xxxxxxxxxx>
>
> The recent commit da278d58a092 "accel: Move Xen accelerator code under
> accel/xen/" introduced a subtle semantic change, making xen_enabled() always
> return false unless CONFIG_XEN is defined prior to inclusion of sysemu/xen.h,
> which appears to be the normal case. This causes various use-cases of QEMU
> with Xen to break.
>
> This patch makes sure that CONFIG_XEN is defined if --enable-xen is passed
> to configure.
>
> Fixes: da278d58a092 ("accel: Move Xen accelerator code under accel/xen/")
> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> ---
> Cc: "Philippe Mathieu-Daudé" <philmd@xxxxxxxxxx>
> Cc: Laurent Vivier <laurent@xxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
> ---
>  configure | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/configure b/configure
> index 2acc4d1465..f1b9d129fd 100755
> --- a/configure
> +++ b/configure
> @@ -7434,6 +7434,7 @@ if test "$virglrenderer" = "yes" ; then
>    echo "VIRGL_LIBS=$virgl_libs" >> $config_host_mak
>  fi
>  if test "$xen" = "yes" ; then
> +  echo "CONFIG_XEN=y" >> $config_host_mak
>    echo "CONFIG_XEN_BACKEND=y" >> $config_host_mak
>    echo "CONFIG_XEN_CTRL_INTERFACE_VERSION=$xen_ctrl_version" >> 
> $config_host_mak
>  fi

Configure already defines CONFIG_XEN as a target-specific
config define in config-target.mak for the specific targets
that Xen will work for (ie if you build --enable-xen for
x86_64-softmmu and ppc64-softmmu then CONFIG_XEN is set for
the former and not the latter). This patch makes it a
build-wide config setting by putting it in config-host.mak.

We should figure out which of those two is correct and do
just one of them, not do both at the same time.

Since CONFIG_HAX, CONFIG_KVM and other accelerator-type
config defines are also per-target, I suspect that the
correct fix for this bug is not in configure but elsewhere.

thanks
-- PMM