linux-kernel - Re: [PATCH v3 5/6] virt, sched: add cpu pinning to smp_call_sync_on_phys

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Date:	Fri, 1 Apr 2016 11:26:25 +0200
From:	Juergen Gross <jgross@...e.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
	konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
	david.vrabel@...rix.com, mingo@...hat.com,
	Douglas_Warzecha@...l.com, pali.rohar@...il.com, jdelvare@...e.com,
	linux@...ck-us.net, tglx@...utronix.de, hpa@...or.com,
	jeremy@...p.org, chrisw@...s-sol.org, akataria@...are.com,
	rusty@...tcorp.com.au, virtualization@...ts.linux-foundation.org,
	x86@...nel.org
Subject: Re: [PATCH v3 5/6] virt, sched: add cpu pinning to
 smp_call_sync_on_phys_cpu()

On 01/04/16 11:15, Peter Zijlstra wrote:
> On Fri, Apr 01, 2016 at 11:03:21AM +0200, Juergen Gross wrote:
>>> Maybe just make the vpin thing an option like:
>>>
>>> 	smp_call_on_cpu(int (*func)(void *), int phys_cpu);
> 
>>> Also; is something like the vpin thing possible on KVM? because if we're
>>> going to expose it to generic code like this we had maybe look at wider
>>> support.
>>
>> It is necessary for dom0 under Xen. I don't think there is a need to do
>> this on KVM as a guest has no direct access to e.g. BIOS functions of
>> the real hardware and the host system needs no vcpu pinning. I'm not
>> sure about VMWare.
> 
> OK, then can we WARN if .phys=1 and the platform doesn't support it?
> 

Yes, good idea.


Juergen