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From: Dario Faggioli <dario.faggioli@citrix.com>
To: Julien Grall <julien.grall@arm.com>,
	George Dunlap <george.dunlap@citrix.com>,
	Stefano Stabellini <sstabellini@kernel.org>
Cc: Juergen Gross <jgross@suse.com>, Peng Fan <peng.fan@nxp.com>,
	Steve Capper <Steve.Capper@arm.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Punit Agrawal <punit.agrawal@arm.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Jan Beulich <jbeulich@suse.com>, Peng Fan <van.freenix@gmail.com>
Subject: Re: [RFC 0/5] xen/arm: support big.little SoC
Date: Thu, 22 Sep 2016 18:31:46 +0200	[thread overview]
Message-ID: <1474561906.4393.395.camel@citrix.com> (raw)
In-Reply-To: <7b87557d-39ee-0b1d-7163-00317571569f@arm.com>


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On Thu, 2016-09-22 at 12:24 +0100, Julien Grall wrote:
> On 22/09/16 09:43, Dario Faggioli wrote:
> > Local migration basically --from the vcpu perspective-- means
> > create a
> > new vcpu, stop the original vcpu, copy the state from original to
> > new,
> > destroy the original vcpu and start the new one. My point is that
> > this
> > is not something that can be done within nor initiated by the
> > scheduler, e.g., during a context switch or a vcpu wakeup!
> 
> By local migration, I meant from the perspective of the hypervisor.
> In 
> the hypervisor you have to trap feature registers and other 
> implementation defined registers to show the same value across all
> the 
> physical CPUs.
> 
You mean we trap feature registers during the (normal) execution of a
vcpu, because we want Xen to vet what's returned to the guest itself.
And that migration support, and hence the possibility that the guest
have been migrated to a cpu different than the one where it was
created, is already one of the reasons why this is necessary... right?

If yes, and if that's "all" we need, I think it should be fine.

> You don't need to recreate the vCPU every time you move from one set
> of 
> CPUs to another one. Sorry for the confusion.
> 
No, I am sorry... it's not you that you're making confusion, it's
probably me knowing to few about ARM, and did not think at the above
when you said "migration". :-)

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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  reply	other threads:[~2016-09-22 16:31 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-19  2:08 [RFC 0/5] xen/arm: support big.little SoC van.freenix
2016-09-19  2:08 ` [RFC 1/5] xen/arm: domain_build: setting opt_dom0_max_vcpus according to cpupool0 info van.freenix
2016-09-19  2:08 ` [RFC 2/5] xen: cpupool: introduce cpupool_arch_info van.freenix
2016-09-19  2:08 ` [RFC 3/5] xen: cpupool: add arch cpupool hook van.freenix
2016-09-19  2:08 ` [RFC 4/5] xen/arm: move vpidr from arch_domain to arch_vcpu van.freenix
2016-09-19  2:08 ` [RFC 5/5] xen/arm: cpupool: implement arch_domain_cpupool_compatible van.freenix
2016-09-19  8:09 ` [RFC 0/5] xen/arm: support big.little SoC Julien Grall
2016-09-19  8:36   ` Peng Fan
2016-09-19  8:53     ` Julien Grall
2016-09-19  9:38       ` Peng Fan
2016-09-19  9:59         ` Julien Grall
2016-09-19 13:15           ` Peng Fan
2016-09-19 20:56             ` Stefano Stabellini
2016-09-19  9:45       ` George Dunlap
2016-09-19 10:06         ` Julien Grall
2016-09-19 10:23           ` Juergen Gross
2016-09-19 17:18             ` Dario Faggioli
2016-09-19 21:03               ` Stefano Stabellini
2016-09-19 22:55                 ` Dario Faggioli
2016-09-20  0:01                   ` Stefano Stabellini
2016-09-20  0:54                     ` Dario Faggioli
2016-09-20 10:03                       ` Peng Fan
2016-09-20 10:27                         ` George Dunlap
2016-09-20 15:34                           ` Julien Grall
2016-09-20 17:24                             ` Dario Faggioli
2016-09-20 19:09                             ` Stefano Stabellini
2016-09-20 19:41                               ` Julien Grall
2016-09-20 20:17                                 ` Stefano Stabellini
2016-09-21  8:38                                   ` Peng Fan
2016-09-21  9:22                                     ` George Dunlap
2016-09-21 12:35                                       ` Peng Fan
2016-09-21 15:00                                       ` Dario Faggioli
2016-09-21 10:15                                     ` Julien Grall
2016-09-21 12:28                                       ` Peng Fan
2016-09-21 15:06                                         ` Dario Faggioli
2016-09-22  9:45                                       ` Peng Fan
2016-09-22 11:21                                         ` Julien Grall
2016-09-23  2:38                                           ` Peng Fan
2016-09-21 10:09                                   ` Julien Grall
2016-09-21 10:22                                     ` George Dunlap
2016-09-21 13:06                                       ` Julien Grall
2016-09-21 15:45                                         ` Dario Faggioli
2016-09-21 19:28                                           ` Julien Grall
2016-09-22  6:16                                             ` Peng Fan
2016-09-22  8:43                                             ` Dario Faggioli
2016-09-22 11:24                                               ` Julien Grall
2016-09-22 16:31                                                 ` Dario Faggioli [this message]
2016-09-23 13:56                                                   ` Julien Grall
2016-09-21 18:13                                         ` Stefano Stabellini
2016-09-21 19:11                                           ` Julien Grall
2016-09-21 19:21                                             ` Julien Grall
2016-09-21 23:45                                             ` Stefano Stabellini
2016-09-22  6:49                                             ` Peng Fan
2016-09-22  8:50                                               ` Dario Faggioli
2016-09-22  9:27                                                 ` Peng Fan
2016-09-22  9:51                                                   ` George Dunlap
2016-09-22 10:09                                                     ` Peng Fan
2016-09-22 10:39                                                       ` Dario Faggioli
2016-09-22 10:13                                                     ` Juergen Gross
2016-09-22  9:52                                                   ` Dario Faggioli
2016-09-22 11:29                                                   ` Julien Grall
2016-09-22 17:31                                                     ` Stefano Stabellini
2016-09-22 18:54                                                       ` Julien Grall
2016-09-23  2:14                                                         ` Peng Fan
2016-09-23  9:24                                                           ` Julien Grall
2016-09-23 10:05                                                             ` Peng Fan
2016-09-23 10:15                                                               ` Julien Grall
2016-09-23 13:36                                                                 ` Dario Faggioli
2016-09-24  1:57                                                                   ` Stefano Stabellini
2016-09-23 13:52                                                               ` Dario Faggioli
2016-09-24  1:35                                                         ` Stefano Stabellini
2016-09-23  2:03                                                     ` Peng Fan
2016-09-22 10:05                                                 ` Peng Fan
2016-09-22 16:26                                                   ` Dario Faggioli
2016-09-22 17:33                                                     ` Stefano Stabellini
2016-09-21 12:38                                     ` Peng Fan
2016-09-21  9:45                         ` Dario Faggioli
2016-09-20 10:18                     ` George Dunlap
2016-09-19 20:55             ` Stefano Stabellini
2016-09-19 10:33           ` George Dunlap
2016-09-19 13:33             ` Peng Fan
2016-09-20  0:11               ` Dario Faggioli
2016-09-20  6:18                 ` Peng Fan
2016-09-19 16:43             ` Dario Faggioli
2016-09-19 13:08       ` Peng Fan

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