From: Ian Jackson <Ian.Jackson@eu.citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Juergen Gross <jgross@suse.com>,
xen-devel@lists.xensource.com, Wei Liu <wei.liu2@citrix.com>,
George Dunlap <george.dunlap@eu.citrix.com>,
Dario Faggioli <dario.faggioli@citrix.com>,
Tim Deegan <tim@xen.org>, Jan Beulich <jbeulich@suse.com>
Subject: Re: [PATCH 3/3] xen: Document XEN_SYSCTL_CPUPOOL_OP_RMCPU anomalous EBUSY result
Date: Thu, 14 Apr 2016 18:56:44 +0100 [thread overview]
Message-ID: <22287.55772.931614.61945@mariner.uk.xensource.com> (raw)
In-Reply-To: <570FD25B.3060802@citrix.com>
Andrew Cooper writes ("Re: [Xen-devel] [PATCH 3/3] xen: Document XEN_SYSCTL_CPUPOOL_OP_RMCPU anomalous EBUSY result"):
> On 14/04/16 18:07, Ian Jackson wrote:
> > +/*
> > + * cpupool operations may return EBUSY if the operation cannot be
> > + * executed right now because of another cpupool operation which is
> > + * still in progress. In this case, EBUSY means that the failed
> > + * operation had no effect.
> > + *
> > + * Some operations including at least RMCPU (xxx which others?) may
> > + * also return EBUSY because a guest has temporarily pinned one of its
> > + * vcpus to the pcpu in question. It is the pious hope (xxx) of the
> > + * author of this comment that this can only occur for domains which
> > + * have been granted some kind of hardware privilege (eg passthrough).
>
> Any VM can be given any arbitrary pinning in its xl configuration file.
> Any arbitrary pinning can be applied at runtime via `xl vcpu-pin ...`
Does that produce EBUSY as well ?
The reuse of the same error number for all of
"the existing configuration (eg toolstack-selected vcpu pinning)
means that the operation does not make sense"
"there is some lock contention and trying again may help"
"a semantically conflicting, or nearly-semantically-conflicting,
operation is currently in progress"
"the guest has done a temporary pin which prevents this operation"
is very unfortunate. How is a toolstack to know what to do ?
> (To the best of my knowledge) A VM cannot choose pinning of its own
> accord. (i.e. the host admin has to choose the pinning.)
AIUI, that is not (now) true.
Ian.
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next prev parent reply other threads:[~2016-04-14 17:56 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-14 17:07 [PATCH 0/3] Revert xc cpupool retries and document anomaly Ian Jackson
2016-04-14 17:07 ` [PATCH 1/3] libxc: Revert "do some retries in xc_cpupool_removecpu() for EBUSY case" Ian Jackson
2016-04-15 5:15 ` Juergen Gross
2016-04-15 7:46 ` Dario Faggioli
2016-04-14 17:07 ` [PATCH 2/3] xen: hypercall docs annotations for xen_sysctl_cpupool_op Ian Jackson
2016-04-14 20:37 ` Dario Faggioli
2016-04-15 10:27 ` Ian Jackson
2016-04-14 17:07 ` [PATCH 3/3] xen: Document XEN_SYSCTL_CPUPOOL_OP_RMCPU anomalous EBUSY result Ian Jackson
2016-04-14 17:24 ` Andrew Cooper
2016-04-14 17:56 ` Ian Jackson [this message]
2016-04-14 20:22 ` Dario Faggioli
2016-04-15 10:20 ` Ian Jackson
2016-04-15 10:43 ` Juergen Gross
2016-04-15 10:58 ` Dario Faggioli
2016-04-15 11:37 ` Juergen Gross
2016-04-15 13:20 ` Juergen Gross
2016-04-15 13:33 ` Dario Faggioli
2016-04-15 14:11 ` Ian Jackson
2016-04-15 14:39 ` Juergen Gross
2016-04-15 5:35 ` Juergen Gross
2016-04-15 7:42 ` Dario Faggioli
2016-04-15 14:12 ` Ian Jackson
2016-04-15 14:17 ` Konrad Rzeszutek Wilk
2016-04-15 14:34 ` Juergen Gross
2016-04-15 14:44 ` Ian Jackson
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