From: Thomas Huth <thuth@redhat.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>,
David Hildenbrand <david@redhat.com>,
qemu-devel@nongnu.org
Cc: qemu-s390x@nongnu.org, Janosch Frank <frankja@linux.ibm.com>,
Cornelia Huck <cohuck@redhat.com>,
Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH v1] s390x/tod: properly stop the KVM TOD while the guest is not running
Date: Tue, 27 Nov 2018 14:06:46 +0100 [thread overview]
Message-ID: <55d945eb-a9ba-9183-9c47-3a1e505d2d35@redhat.com> (raw)
In-Reply-To: <f31fb9d1-d1dd-7d06-7993-08e44bb77632@de.ibm.com>
On 2018-11-27 13:43, Christian Borntraeger wrote:
> On 27.11.2018 12:41, David Hildenbrand wrote:
>> Just like on other architectures, we should stop the clock while the guest
>> is not running. This is already properly done for TCG. Right now, doing an
>> offline migration (stop, migrate, cont) can easily trigger stalls in the
>> guest.
>>
>> Even doing a
>> (hmp) stop
>> ... wait 2 minutes ...
>> (hmp) cont
>> will already trigger stalls.
>>
>> So whenever the guest stops, backup the KVM TOD. When continuning to run
>> the guest, restore the KVM TOD.
>
> We do a similar thing for managedsave so it probably makes sense to solve
> the stall warnings. Now: At the same time, we actually want to have the guest
> see the real time and maybe even share the TOD clock with the host in some
> way, while at the same time avoid the stall warnings.
Hmm, by the way, do we also have to consider the "-rtc clock=host|rt|vm"
option from the commandl line, or is this an orthogonal concept?
Thomas
next prev parent reply other threads:[~2018-11-27 13:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 11:41 [Qemu-devel] [PATCH v1] s390x/tod: properly stop the KVM TOD while the guest is not running David Hildenbrand
2018-11-27 12:19 ` Thomas Huth
2018-11-27 12:50 ` David Hildenbrand
2018-11-27 13:03 ` Thomas Huth
2018-11-27 12:38 ` Cornelia Huck
2018-11-27 12:50 ` David Hildenbrand
2018-11-27 13:17 ` David Hildenbrand
2018-11-27 12:43 ` Christian Borntraeger
2018-11-27 12:48 ` Cornelia Huck
2018-11-27 12:59 ` David Hildenbrand
2018-11-27 13:06 ` Thomas Huth [this message]
2018-11-27 13:11 ` Christian Borntraeger
2018-11-27 13:16 ` David Hildenbrand
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