Re: Building armel on arm64
Apologies for delayed response - I've been horrendously busy. :-/
On Sun, Jul 08, 2018 at 11:03:12PM +0300, Adrian Bunk wrote:
>On Wed, Jun 27, 2018 at 08:03:00PM +0000, Niels Thykier wrote:
>>...
>> armel/armhf:
>> ------------
>>
>> * Undesirable to keep the hardware running beyond 2020. armhf VM
>> support uncertain. (DSA)
>>...
>
>I'd like to get a clear picture regarding the situation of building
>armel for buster on arm64, ideally moving it to arm64 hardwre soon.
ACK.
>1. What issues are considered possible problems for moving building
> armel from 32bit v7 hardware to 64bit v8 hardware?
>
>ARM has some history of adding new functionality in new versions of
>their architecture that gets deprecated in the next version of their
>architecture.
>
>The armel baseline (currently armv5te) is low enough that several
>of the issues with running armhf code on arm64 are not present
>when running armel code on arm64.
>
>If anyone sees potential blockers for building armel on arm64,
>especially ones that are not present for building armhf on arm64,
>please speak up now.
I was worried about CP15 barriers, but I've been digging in docs for a
while and can't find anything to back that up for v5.
>2. What level of testing has been done before building armhf on arm64?
>
>64bit arm-arm-01 has started participating in building armhf for
>unstable and experimental.
>
>I don't want to do less testing for armel than has been done for armhf
>prior to doing that, what testing had been done for armhf on arm64
>building prior to doing it on a buildd?
Not very much *so far*. I wsan't expecting to find any issues, but at
least two clear issues have shown up so far:
* Alignment fixups. We have these enabled on our v7 buildds, but
there is no support for this at all in the arcm64 kernel. See
#902990 as an example.
* The definitions for MINSIGSTKSZ differ between armhf and arm64 -
see #904385
To get an idea about these and any other problems, I've started a mass
rebuild of the archive as armhf-on-arm64 on three machines at
home. They're currently ~40% of the way through the archive and I
estimate they are going to take another couple of weeks to complete.
The next big problem I can see is in our haskell packages for
armhf. From my build log for haskell-zxcvbn-c_1.0.1-4.log (as an
example):
...
Setting up llvm-3.9 (1:3.9.1-19+b1) ...
Setting up ghc (8.2.2-4) ...
Illegal instruction
update-alternatives: using /usr/bin/ghc to provide /usr/bin/haskell-compiler (haskell-compiler) in auto mode
Illegal instruction
dpkg: error processing package ghc (--configure):
installed ghc package post-installation script subprocess returned error exit status 132
...
I'm going to have a look at that later today.
>3. Starting to build armel on arm64
>
>Depending on the answers to the questions above I would like to
>setup building armel on arm64, perhaps on the same arm-arm-01.
Possibly. Let's see how things go - I'm looking at sourcing many more
machines too...
--
Steve McIntyre, Cambridge, UK. steve@einval.com
"I can't ever sleep on planes ... call it irrational if you like, but I'm
afraid I'll miss my stop" -- Vivek Das Mohapatra
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