Indeed. ARMv7 adds some pretty fundamental instructions (v6 was the first to do SMP) that we rely on, particularly more optimized address calculation, atomic reservation engine support, and a whole host of other extensions. The system model also differs dramatically going backward. -- Sent from my iPad Ignoring FPU, ARMv7 binaries in general cannot run on an ARMv5 processor.
On Aug 5, 2013 12:02 PM, "Kyle McMartin" < kyle@xxxxxxxxxx> wrote:
On Mon, Aug 05, 2013 at 10:51:21AM -0500, Alex Villacís Lasso wrote:
> 1) In /proc/cpuinfo, I have seen the "vfp" flag. Does this stand for "vector floating point", a FPU? Could there be other kinds of FPU that might be reported as different flags?
Yes, but there's several variants of VFP provided by ARM cpus.
> 2) If an ARM chipset that is officially armv5tel can be guaranteed
> to have a FPU (vfp or otherwise), can it boot an armv7hl userspace
> with the same custom-built armv5tel kernel it used before? Do I have
> to watch out for specific kernel compile options before attempting
> this?
Broadly speaking "maybe" armv7hl requires vfp3-16, which is v3 VFP but
with only 16 registers, and not the full 32, so that we support marvell
and tegra chips. armv5tel only provides vfp2, which is missing some
vfp convert instructions. I suppose it would be possible to emulate them
but you're probably better off using pidora or rebuilding yourself.
--Kyle
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