[PATCH] arm64: defconfig: add options for virtualization and containers

[Catalin Marinas]

On Tue, May 31, 2016 at 02:57:41PM +0100, Will Deacon wrote:
> On Fri, May 27, 2016 at 01:42:27PM +0300, Riku Voipio wrote:
> > Enable options commonly needed by popular virtualization
> > and container applications. Use modules when possible to
> > avoid too much overhead for users not interested.
> > 
> > - add namespace and cgroup options needed
> > - add seccomp - optional, but enhances Qemu etc
> > - bridge, nat, veth, macvtap and multicast for routing
> >   guests and containers
> > - btfrs and overlayfs modules for container COW backends
> > - while near it, make fuse a module instead of built-in.
> > 
> > Generated with make saveconfig and dropping unrelated spurious
> > change hunks while commiting. bloat-o-meter old-vmlinux vmlinux:
> > 
> > add/remove: 899/388 grow/shrink: 744/216 up/down: 183556/-94881 (88675)
> > ...
> > Total: Before=10515333, After=10604008, chg 0.000000%
> > 
> > Signed-off-by: Riku Voipio <riku.voipio at linaro.org>
> > ---
> >  arch/arm64/configs/defconfig | 53 +++++++++++++++++++++++++++++++++++++++-----
> >  1 file changed, 47 insertions(+), 6 deletions(-)
> 
> I'm fine with adding stuff to defconfig if it's useful to people (and it
> looks like this is), but it's probably about time we figured out what to
> do about '=y' vs '=m'. Until recently (i.e. this merge window), the arm64
> defconfig didn't build any modules. Obviously this only scales so far,
> since the Image tends to get rather huge, but it would be good to try and
> establish a rule-of-thumb as to whether we treat something as a module
> or a built-in. We could even consider retrospectively applying the rule
> if its straightforward enough.
> 
> One easy way to do it would be: if you need the option to boot, then
> it's a built-in, but that brings up questions around "boot a full android
> system" vs "boot to a point where you could load an initrd".

For the time being, I would say defconfig should cover "boot to a login
prompt" where this may imply NFS + network driver built in for the
supported SoCs, couple of commonly used filesystems (ext4, btrfs). The
rest can be enabled as modules.

As the image continues to grow over years, we will have to revisit this
and possibly separate the mobile from the server SoC defconfig. For the
former, we can probably keep the same "boot to a login prompt" approach.
For the latter, especially if you install it under a distro (e.g. you do
make deb-pkg or rpm-pkg), we can aim for "boot to initramfs". That said,
I'd like to see most of the SoC drivers stuff built as modules (whatever
is not essential for booting to initramfs and comes in at
device_initcall level).

-- 
Catalin