Bug 1161707 - max CPUs exceeded for cross build aarch64
Summary: max CPUs exceeded for cross build aarch64
Status: NEW
Alias: None
Product: openSUSE.org
Classification: openSUSE
Component: BuildService (show other bugs)
Version: unspecified
Hardware: Other Other
: P5 - None : Minor (vote)
Target Milestone: ---
Assignee: Adrian Schröter
QA Contact: Adrian Schröter
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Reported: 2020-01-23 14:32 UTC by Christian Goll
Modified: 2020-01-24 11:18 UTC (History)
1 user (show)

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Description Christian Goll 2020-01-23 14:32:12 UTC 
When cross building on x86_64 12 cores (24 hw threads) machine for aarch64, with the command:
osc build openSUSE_Factory_ARM --vm-type=qemu aarch64
I get following error message:
qemu-system-aarch64: Number of SMP CPUs requested (24) exceeds max CPUs supported by machine 'mach-virt' (8)
the osc version is 0.167.2
This may also be a bug in qemu-system-aarch64, but then there should be an option for the number of virtual CPUs in osc.

P.S.
I saw that the description says:
build.opensuse.org instance itself -- Build Service is an own product in bugzilla otherwise
but I could not find the product in bugzilla.opensuse.org
Comment 1 Egbert Eich 2020-01-23 17:21:33 UTC 
If qemu-system-aarch64 has a hard limit of CPUs, 'osc build' should actually take this into account.
@Antoine: do you happen to know if there is a way to determine this limit before trying to run qemu with a higher number?
Comment 2 Adrian Schröter 2020-01-24 07:47:50 UTC 
Does it help to add    gic-version=host     on qemu run?

(You should be able to see the qemu call in the log, just copy and paste)
Comment 3 Antoine Ginies 2020-01-24 11:06:03 UTC 
(In reply to Egbert Eich from comment #1)
> If qemu-system-aarch64 has a hard limit of CPUs, 'osc build' should actually
> take this into account.
> @Antoine: do you happen to know if there is a way to determine this limit
> before trying to run qemu with a higher number?

I don't think there is a way to get this information from QEMU, its in the headers when building it as far as i know.
We do not recomment more than 8x per real core.
Comment 4 Antoine Ginies 2020-01-24 11:18:31 UTC 
(In reply to Antoine Ginies from comment #3)
> (In reply to Egbert Eich from comment #1)
> > If qemu-system-aarch64 has a hard limit of CPUs, 'osc build' should actually
> > take this into account.
> > @Antoine: do you happen to know if there is a way to determine this limit
> > before trying to run qemu with a higher number?
> 
> I don't think there is a way to get this information from QEMU, its in the
> headers when building it as far as i know.
> We do not recomment more than 8x per real core.

I quickly look to find the info, and there is no no limit define exept for special scenario like doing XEN HVM XEN :32 vcpu.