Re: [Xen-devel] [XEN PATCH for-4.13] tools/configure: Honour XEN_COMPILE_ARCH and _TARGET_ for shim

[Wei Liu <wl@xxxxxxx>]

On Tue, 19 Nov 2019 at 16:47, Ian Jackson <ian.jackson@xxxxxxxxxx> wrote:
[...]
>
> > >From 1a8de36699b9042c30797e05f7a5f4313d7f7ad1 Mon Sep 17 00:00:00 2001
> > From: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > Date: Tue, 29 Oct 2019 17:45:30 +0000
> > Subject: [PATCH] tools/configure: Honour XEN_COMPILE_ARCH and _TARGET_ for
> >  shim
> > MIME-Version: 1.0
> > Content-Type: text/plain; charset=UTF-8
> > Content-Transfer-Encoding: 8bit
> >
> > The pvshim can only be built 64-bit because the hypervisor is only
> > 64-bit nowadays.  The hypervisor build supports XEN_COMPILE_ARCH and
> > XEN_TARGET_ARCH which override the information from uname.  The pvshim
> > build runs out of the tools/ directory but calls the hypervisor build
> > system.
> >
> > If one runs in a Linux 32-bit userland with a 64-bit kernel, one used
> > to be able to set XEN_COMPILE_ARCH.  But nowadays this does not work.
> > configure sees the target cpu as 64-bit and tries to build pvshim.
> > The build prints
> >   echo "*** Xen x86/32 target no longer supported!"
> > and doesn't build anything.  Then the subsequent Makefiles try to
> > install the non-built pieces.
> >
> > Fix this anomaly by causing configure to honour the Xen hypervisor way
> > of setting the target architecture.
> >
> > In principle this user behaviour is not handled quite right, because
> > configure will still see 64-bit and so all the autoconf-based
> > architecture testing will see 64-bit rather than 32-bit x86.  But the
> > tools are in fact generally quite portable: this particular location
> > in configure{.ac,} is the only place in tools/ where 64-bit x86 is
> > treated differently from 32-bit x86, so the fix is sufficient and
> > correct for this use case.
> >
> > It remains the case that XEN_COMPILE_ARCH or XEN_TARGET_ARCH to a
> > non-x86 architecture, when configure thinks things are x86, or vice
> > versa, will not work right.
> >
> > (This is a bugfix to 8845155c831c
> >   pvshim: make PV shim build selectable from configure
> > which inadvertantly deleted the logic to only build the shim for
> > XEN_TARGET_ARCH != x86_32.)
> >
> > I have rerun autogen.sh, so this patch contains the fix to configure
> > as well as the source fix to configure.ac.
> >
> > Fixes: 8845155c831c59e867ee3dd31ee63e0cc6c7dcf2
> > Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > CC: Olaf Hering <olaf@xxxxxxxxx>
> > CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > Release-acked-by: Jürgen Groß <jgross@xxxxxxxx>

Reviewed-by: Wei Liu <wl@xxxxxxx>

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