Re: [PATCH v2] docs/devel: Add cross-compiling doc

[Andrew Jones]

On Thu, Sep 07, 2023 at 02:31:20PM +0200, Andrew Jones wrote:
> On Thu, Sep 07, 2023 at 11:20:55AM +0100, Alex Bennée wrote:
> > 
> > Andrew Jones <ajones@ventanamicro.com> writes:
> > 
> > > Add instructions for how to cross-compile QEMU for RISC-V. The
> > > file is named generically because there's no reason not to collect
> > > other architectures steps into the same file, especially because
> > > several subsections like those for cross-compiling QEMU dependencies
> > > using meson and a cross-file could be shared. Additionally, other
> > > approaches to creating sysroots, such as with debootstrap, may be
> > > documented in this file in the future.
> > >
> > > Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
> > > ---
> > >  docs/devel/cross-compiling.rst | 221 +++++++++++++++++++++++++++++++++
> > >  docs/devel/index-build.rst     |   1 +
> > >  2 files changed, 222 insertions(+)
> > >  create mode 100644 docs/devel/cross-compiling.rst
> > >
> > > diff --git a/docs/devel/cross-compiling.rst 
> > > b/docs/devel/cross-compiling.rst
> > > new file mode 100644
> > > index 000000000000..1b988ba54e4c
> > > --- /dev/null
> > > +++ b/docs/devel/cross-compiling.rst
> > > @@ -0,0 +1,221 @@
> > > +.. SPDX-License-Identifier: GPL-2.0-or-later
> > > +
> > > +====================
> > > +Cross-compiling QEMU
> > > +====================
> > > +
> > > +Cross-compiling QEMU first requires the preparation of a cross-toolchain
> > > +and the cross-compiling of QEMU's dependencies. While the steps will be
> > > +similar across architectures, each architecture will have its own 
> > > specific
> > > +recommendations.
> > 
> > "some architectures" - most of the cross compile stuff is hidden away by
> > the build system on systems with appropriate development libraries
> > installed. I think we would be remiss if we didn't just outline the
> > common case:
> > 
> >    ../configure --cross-prefix=riscv64-linux-gnu-
> > 
> > I think we could make it clearer that in most cases you don't need to
> > prepare and cross-compile a bunch of dependencies lest we send
> > developers down a rabbit hole.
> > 
> > Maybe build-system.rst be updated and this reference it for the common
> > case?
> > 
> 
> Hi Alex,
> 
> tl;dr, I'd welcome instructions helping people get cross-arch development
> libraries installed without having to build them. I wouldn't make a good
> author for those instructions, though, since I don't know how.
> 
> I'm guessing the dependencies can be installed with a distro's package
> management, assuming the package management supports cross-arch
> installation and installing to a specified root directory. I'm on Fedora,
> so I just tried
> 
>  $ sudo dnf install --forcearch=aarch64 --installroot=$SYSROOT 
> --releasever=36 glib2-devel
> 
> but it wanted to install a huge number of packages, which most people
> probably wouldn't want to do. Maybe that command isn't what you had in
> mind or other distros can manage this better. I'm all ears.
>

Ah, I just saw your other reply on the original posting. The magic is in
docker stuff.

I'll look into it, but I'd also make a poor author for anything regarding
docker :-)

Thanks,
drew