[fedora-arm] Re: armhf dnf is not working on aarch64 kernel

On Wed, 27 Apr 2016 22:31:09 +0900
Chanho Park <parkch98@gmail.com> wrote:

> Hi,
>
> On Wednesday, April 27, 2016, Peter Robinson <pbrobinson@gmail.com> wrote:
>
> > On Wed, Apr 27, 2016 at 2:09 PM, Chanho Park <parkch98@gmail.com
> > <javascript:;>> wrote:
> > > Hi Peter,
> > >
> > > On Wednesday, April 27, 2016, Peter Robinson <pbrobinson@gmail.com
> > <javascript:;>> wrote:
> > >>
> > >> On Wed, Apr 27, 2016 at 1:18 PM, Chanho Park <parkch98@gmail.com
> > <javascript:;>> wrote:
> > >> > Hi all,
> > >> >
> > >> > I want to use the armhf fedora rootfs on the aarch64 bit kernel.
> > >>
> > >> You can't, it's not a use case we support.
> > >>
> > > Why not? All arm binaries can be runnable on aarch32 mode of aarch64
> > kernel.
> >
> > Not exactly actually, it's possible to have aarch64/ARMv8 CPUs that
> > don't have the 32 bit components.
> >
> > >> > The question is 'how can I run 'dnf' command on armhf fedora with
> > >> > aarch64 kernel?'
> > >>
> > >> No, the ARMv7 and aarch64 ABI aren't compatible, the only way we
> > >> support ARMv7 on aarch64 is via virtualisation. We will not be
> > >> supporting this or a "multilib" usecase.
> > >
> > >
> > > The aarch64 kernel can execute both aarch64 and aarch32(fully compatible
> > > armv7) binaries. For example, the kernel of raspberry pi 3 is aarch64 and
> > > fedora arm version can't run on rpi3. Even all binaries can run on it but
> > > only dnf command can't do that.
> >
> > Actually that isn't entirely true. The kernel that's currently shipped
> > in raspbian for RPi3 is actually an ARMv7 kernel where the firmware
> > boots the ARM cores as v7 cores. The kernel code that's running there
> > is ARMv7 code not cortex-a53 code paths. That is a fairly special
> > usecase and you can actually do that on Fedora ARMv7 with a Fedora
> > ARMv7 kernel, not a aarch64 kernel.
>
> Ah. Sorry. It's not good example. Actually, rpi3 try to enable aarch64
> kernel but they can't di that lack of time. (
> https://www.linux.com/news/raspberry-pi-3-still-essentially-32-bit-sbc-now)
> Pine64 is also available cheap board which kernel is aarch64 version.
>
>
> > ARM multilib is something we explicitly decided not to support when we
> > were dealing with that. Multilib is a mess on x86, it's not a mess we
> > need on ARM.
>
>
> No. It's not multilib. I want to run _only_ armv7 binaries and libraries. I
> want to know why only 'dnf' is impossible do that.

leaving the Fedora design question out, it's because dnf does not
consider aarch64 and armhfp as compatible arches. That's something dnf
project can eventually solve.

If I understand the use-case, it's the same as one would run full i686
userspace with x86_64 kernel (s390 on s390x kernel). I think there were
such attempts.

Dan
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