On Thu, Jul 26, 2018 at 09:44:11AM +0200, Laurent Vivier wrote: > On 26/07/2018 07:07, David Gibson wrote: > > On Thu, May 03, 2018 at 11:20:44PM -0500, Michael Roth wrote: > >> In some cases (e.g. spapr) we record guest timebase after qmp_stop() > >> via a runstate hook so we can restore it on qmp_cont(). If a migration > >> occurs in between those events we end up saving it again, this time > >> based on the current timebase the guest would be seeing had it been > >> running. This has the effect of advancing the guest timebase while > >> it is stopped, which is not what the code intends. > >> > >> Other than simple jumps in time, this has been seen to trigger what > >> appear to be RCU-related crashes in recent kernels when the advance > >> exceeds rcu_cpu_stall_timeout, and it can be triggered by fairly > >> common operations such as `virsh migrate ... --timeout 60`. > >> > >> Cc: Alexey Kardashevskiy <a...@ozlabs.ru> > >> Cc: David Gibson <da...@gibson.dropbear.id.au> > >> Cc: Laurent Vivier <lviv...@redhat.com> > >> Cc: qemu-...@nongnu.org > >> Cc: qemu-sta...@nongnu.org > >> Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com> > > > > Sorry, this fell off my radar for ages, but I've finally had a chance > > to look at it properly. > > > > I'm not totally convinced this handle all the possible edge cases > > correctly, but I am convinced it gives behaviour that's more correct > > than we have now. It doesn't introduce changes to the interface or > > migration stream that would break things in future, so I've applied it > > to ppc-for-3.1. > > See https://bugzilla.redhat.com/show_bug.cgi?id=1571230#c8 > > So you revert: > > commit 42043e4f1241eeb77f87f5816b5cf0b6e9583ed7 > Author: Laurent Vivier <lviv...@redhat.com> > Date: Fri Jan 27 13:24:58 2017 +0100 > > spapr: clock should count only if vm is running > > and change the behaviour compared to x86_64 > > 6053a86 kvmclock: reduce kvmclock difference on migration > > Is this what you want?
Ah, no, not really. I've pulled it out of 3.1 again. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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