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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Nov 12, 2019 at 11:57:32AM +0000, Ian Jackson wrote:
> Ian Jackson writes ("Re: [Xen-devel] [XEN PATCH for-4.13] tools/configure: 
> Honour XEN_COMPILE_ARCH and _TARGET_ for shim"):
> > Andrew Cooper writes ("Re: [Xen-devel] [XEN PATCH for-4.13] 
> > tools/configure: Honour XEN_COMPILE_ARCH and _TARGET_ for shim"):
> > > On 29/10/2019 17:57, Ian Jackson wrote:
> > > > 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.
> > > 
> > > This looks to be a bugfix to 8845155c831c59e867ee3dd31ee63e0cc6c7dcf2 ?
> > > 
> > > In particular, this deleted the logic to only build the shim for
> > > XEN_TARGET_ARCH != x86_32.
> > 
> > Yes.  I have added a note about that to the commit message (stealing
> > your text, thanks) and now I am CCing the author and requester of that
> > commit, for form's sake.
> 
> Andrew, did you want to ack this ?  Or do you have further comments ?
> I have a release-ack...
> 
> Thanks,
> Ian.
> 
> 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>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks.

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