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From: Dario Faggioli <dfaggioli@suse.com>
To: Julien Grall <julien.grall@arm.com>,
	Mirela Simonovic <mirela.simonovic@aggios.com>
Cc: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Davorin Mista <dm@aggios.com>,
	Xen Devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH v3 10/10] xen/arm: Enable errata for secondary CPU on hotplug after the boot
Date: Fri, 11 May 2018 15:12:53 +0200	[thread overview]
Message-ID: <51bc496593c99d77909dd5193dd2c9c0c969667e.camel@suse.com> (raw)
In-Reply-To: <51febc3c-c55a-6512-1d32-0d2bb0a64df7@arm.com>


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On Fri, 2018-05-11 at 11:54 +0100, Julien Grall wrote:
> On 11/05/18 11:41, Mirela Simonovic wrote:
> "We should really avoid to use panic(...) if this is something the 
> system can survive. In that specific case, it would only affect the 
> current CPU. So it would be better to return an error and let the
> caller 
> decide what to do."
> 
> To summarize:
> 	1) Notifiers should only report an error and let the upper
> caller (here 
> notify_cpu_starting()) deciding what to do.
> 	2) I am OK with the BUG_ON in notify_cpu_starting() for now.
> 
And, in general, I agree with all this.

However (and I think I'm repeating this concept for, what, the 10th
time now?!?! :-P), in this specific case, the reason why none of the
existing CPU_STARTING callbacks report an error, is that the CPU
bringup process is, AFAICT, built around the assumption that once we
reached CPU_STARTING, things can't fail.

For this very reason, whatever new CPU_STARTING callback is introduced,
in this series or everywhere else, _can't_ fail, and _can't_ return any
error.

If we need to have a CPU_STARTING callback that can fail, we need to
change the CPU bringup process accordingly.

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Software Engineer @ SUSE https://www.suse.com/

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  parent reply	other threads:[~2018-05-11 13:12 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27 17:12 [PATCH v3 00/10] xen/arm64: Suspend preconditions and CPU hotplug fixes Mirela Simonovic
2018-04-27 17:12 ` [PATCH v3 01/10] xen/arm64: Added handling of the trapped access to OSLSR register Mirela Simonovic
2018-04-27 17:12 ` [PATCH v3 02/10] xen/arm: Ignore write to GICD_ISACTIVERn registers (vgic-v2) Mirela Simonovic
2018-04-30 14:32   ` Julien Grall
2018-04-27 17:12 ` [PATCH v3 03/10] xen/arm: Implement CPU_OFF PSCI call (physical interface) Mirela Simonovic
2018-04-30 14:36   ` Julien Grall
2018-04-27 17:12 ` [PATCH v3 04/10] xen/arm: Remove __initdata and __init to enable CPU hotplug Mirela Simonovic
2018-04-27 17:12 ` [PATCH v3 05/10] xen/arm: Setup virtual paging for non-boot CPUs on hotplug/resume Mirela Simonovic
2018-04-30 14:47   ` Julien Grall
2018-05-07 14:55     ` Mirela Simonovic
2018-05-08 14:14       ` Julien Grall
2018-05-08 14:28         ` Mirela Simonovic
2018-05-09 10:32           ` Julien Grall
2018-04-27 17:12 ` [PATCH v3 06/10] xen/common: Restore IRQ affinity when hotplugging a pCPU Mirela Simonovic
2018-05-10  7:33   ` Dario Faggioli
2018-04-27 17:12 ` [PATCH v3 07/10] xen/arm: Release maintenance interrupt when CPU is hot-unplugged Mirela Simonovic
2018-04-30 14:51   ` Julien Grall
2018-04-27 17:12 ` [PATCH v3 08/10] xen/arm: Release timer interrupts " Mirela Simonovic
2018-04-30 15:58   ` Julien Grall
2018-05-07 15:33     ` Mirela Simonovic
2018-04-27 17:12 ` [PATCH v3 09/10] xen/arm: Free memory allocated for sibling/core maps on CPU hot-unplug Mirela Simonovic
2018-04-30 15:55   ` Julien Grall
2018-04-27 17:12 ` [PATCH v3 10/10] xen/arm: Enable errata for secondary CPU on hotplug after the boot Mirela Simonovic
2018-04-30 16:09   ` Julien Grall
2018-05-09 15:48     ` Mirela Simonovic
2018-05-09 16:32       ` Julien Grall
2018-05-10 11:57         ` Mirela Simonovic
2018-05-10 13:24           ` Mirela Simonovic
2018-05-10 13:29             ` Julien Grall
2018-05-10 14:12               ` Mirela Simonovic
2018-05-10 14:35                 ` Julien Grall
2018-05-10 14:25             ` Dario Faggioli
2018-05-10 15:00               ` Mirela Simonovic
2018-05-10 15:13                 ` Julien Grall
2018-05-10 15:49                   ` Mirela Simonovic
2018-05-10 16:02                     ` Julien Grall
2018-05-10 16:21                       ` Dario Faggioli
2018-05-10 16:24                     ` Dario Faggioli
2018-05-11 10:41                       ` Mirela Simonovic
2018-05-11 10:54                         ` Julien Grall
2018-05-11 12:07                           ` Mirela Simonovic
2018-05-11 12:20                             ` Mirela Simonovic
2018-05-11 13:08                               ` Julien Grall
2018-05-11 13:31                                 ` Dario Faggioli
     [not found]                                   ` <CAKPH-Nj2znmdcjZEfFf83WmrcBS_u4R33yPOxAPWw37RHVZ38g@mail.gmail.com>
2018-05-11 14:14                                     ` Dario Faggioli
2018-05-11 21:47                                   ` Stefano Stabellini
2018-05-14  9:44                                     ` Julien Grall
2018-05-14 16:59                                       ` Stefano Stabellini
2018-05-15 11:45                                         ` Mirela Simonovic
2018-05-11 13:12                           ` Dario Faggioli [this message]
2018-05-11 13:01                         ` Dario Faggioli
2018-05-10 16:12                   ` Dario Faggioli
2018-05-10 13:33           ` Dario Faggioli

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