linux-kernel - Re: [PATCH 1/3] Powerpc: mpc85xx: refactor the PM operations

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Date:	Mon, 3 Aug 2015 15:26:08 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Chenhui Zhao <chenhui.zhao@...escale.com>
CC:	<b29983@...escale.com>, <b07421@...escale.com>,
	<linux-kernel@...r.kernel.org>,
	Tang Yuantian <Yuantian.Tang@...escale.com>,
	Tang Yuantian <Yuantian.Tang@...scale.com>
Subject: Re: [PATCH 1/3] Powerpc: mpc85xx: refactor the PM operations

On Mon, 2015-08-03 at 19:32 +0800, Chenhui Zhao wrote:
> > 

> On Sat, Aug 1, 2015 at 7:59 AM, Scott Wood <scottwood@...escale.com> 
> wrote:

> >
> > Could you explain irq_mask()?  Why would there still be IRQs destined 
> > for
> > this CPU at this point?
> 
> This function just masks irq by setting the registers in RCPM (for 
> example, RCPM_CPMIMR, RCPM_CPMCIMR). Actually, all irqs to this CPU 
> have been migrated to other CPUs.

So why do we need to set those bits in RCPM?  Is it just caution?

> > @@ -431,21 +415,9 @@ void __init mpc85xx_smp_init(void)
> > >                smp_85xx_ops.probe = NULL;
> > >        }
> > > 
> > >  -     np = of_find_matching_node(NULL, mpc85xx_smp_guts_ids);
> > >  -     if (np) {
> > >  -             guts = of_iomap(np, 0);
> > >  -             of_node_put(np);
> > >  -             if (!guts) {
> > >  -                     pr_err("%s: Could not map guts node 
> > > address\n",
> > >  -                                                             
> > > __func__);
> > >  -                     return;
> > >  -             }
> > >  -             smp_85xx_ops.give_timebase = mpc85xx_give_timebase;
> > >  -             smp_85xx_ops.take_timebase = mpc85xx_take_timebase;
> > >   #ifdef CONFIG_HOTPLUG_CPU
> > >  -             ppc_md.cpu_die = smp_85xx_mach_cpu_die;
> > >  +     ppc_md.cpu_die = qoriq_cpu_dying;
> > >   #endif
> > 
> > Shouldn't you make sure there's a valid qoriq_pm_ops before setting
> > cpu_die()?  Or make sure that qoriq_cpu_dying() works regardless.
> > 
> > -Scott
> 
> This patch is just for e500v2. The following patches will handle the 
> case of e500mc, e5500 and e6500.

What stops a user from trying to use cpu hotplug on unsupported cpus, or in a 
virtualized environment, and crashing here?

-Scott

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