On 2016-04-27 14:17, Peter Robinson wrote:
On Wed, Apr 27, 2016 at 2:09 PM, Chanho Park <parkch98@xxxxxxxxx>
wrote:
Hi Peter,
On Wednesday, April 27, 2016, Peter Robinson <pbrobinson@xxxxxxxxx>
wrote:
On Wed, Apr 27, 2016 at 1:18 PM, Chanho Park <parkch98@xxxxxxxxx>
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.
That this is not the case here, though. So the answer doesn't seem
to answer the question.
> 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.
Again, this doesn't answer the question and ignored the most obvious
and common case, where we have ARMv8 hardware (e.g. X-Gene) that fully
supports ARMv7 instruction set for backward compatibility, running an
aarch64 kernel with 4KB memory pages (the sensible size) and backward
compatibility option enabled (no detriment to doing so).
You can then run an armv7hl (or armv5tel) userspace in a chroot with
no ill effects. I run a setup like this where I run hard-float and
soft-float 32-bit userspace docker containers even though the host
userspace and kernels are aarch64. I see no sane reason why this
would not be a supported configuration, since the usefulness of it
seems very obvious.
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.
We aren't talking about multilib here, we are talking about
chroots/containers which are a very separate use case.
But since you mentioned it, if we don't have multilib because it's
a mess, why is it that aarch64 Fedora still uses lib64 rather than
lib directories? I don't see how this is less of a mess than what
we have on x86 at all. It seems we have just as big a mess but
without the feature benefits.
Gordan
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