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From: David Hildenbrand <david@redhat.com>
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Date: Wed, 13 Sep 2017 18:25:10 +0200
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Subject: Re: [Qemu-devel] [PATCH v5 11/22] s390x: allow only 1 CPU with TCG
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To: =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>
Cc: qemu-devel@nongnu.org, Matthew Rosato <mjrosato@linux.vnet.ibm.com>, thuth@redhat.com, Eduardo Habkost <ehabkost@redhat.com>, cohuck@redhat.com, Richard Henderson <richard.henderson@linaro.org>, Alexander Graf <agraf@suse.de>, Markus Armbruster <armbru@redhat.com>, borntraeger@de.ibm.com, Igor Mammedov <imammedo@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

On 13.09.2017 18:13, Alex Benn=C3=A9e wrote:
>=20
> David Hildenbrand <david@redhat.com> writes:
>=20
>> Specifying more than 1 CPU (e.g. -smp 5) leads to SIGP errors (the
>> guest tries to bring these CPUs up but fails), because we don't suppor=
t
>> multiple CPUs on s390x under TCG.
>>
>> Let's bail out if more than 1 is specified, so we don't raise people's
>> hope.
>=20
> Why does this restriction exist? Without MTTCG enabled -smp > 1 should
> be safe from any races.

Because the actual SIGP code (instruction to start/stop ... CPUs) is not
implemented yet.


--=20

Thanks,

David