linux-kernel - Re: [PATCH tip/core/rcu 02/20] x86: Use common outgoing-CPU-notification code

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Message-ID: <54F72E67.1000206@oracle.com>
Date:	Wed, 04 Mar 2015 11:10:15 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	David Vrabel <david.vrabel@...rix.com>, paulmck@...ux.vnet.ibm.com
CC:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com, x86@...nel.org,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH tip/core/rcu 02/20] x86: Use common outgoing-CPU-notification
 code

On 03/04/2015 10:45 AM, David Vrabel wrote:
> On 04/03/15 14:55, Boris Ostrovsky wrote:
>> In the meantime, it turned out that HVM guests are broken by this patch
>> (with our without changes that we've been discussing), because HVM CPUs
>> die with
>>
>> static void xen_hvm_cpu_die(unsigned int cpu)
>> {
>>          xen_cpu_die(cpu);
>>          native_cpu_die(cpu);
>> }
>>
>> Which means that cpu_wait_death() is called twice, and second call moves
>> the CPU to CPU_BROKEN.
>>
>> The simple solution is to stop calling native_cpu_die() above but I'd
>> like to use common code in native_cpu_die(). I'll see if I can carve it
>> out without too much damage to x86.
> If not really been following this thread but...
>
> Would it be preferable to refactor xen_cpu_die() instead to factor out
> its the cpu_wait_death() call?

That's essentially what I was going to do. Except that native_cpu_die() 
returns void so I'll need some common non-void code that lives in x86.

And then we can drop xen_hvm_cpu_die() and use xen_cpu_die() for all guests.

-boris

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