From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <jgross@suse.com>
Subject: Re: [Xen-devel] [PATCH v2 5/6] virt, sched: add cpu pinning to
	smp_call_sync_on_phys_cpu()
Date: Mon, 21 Mar 2016 15:21:04 +0100
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To: Jan Beulich <JBeulich@suse.com>
Cc: jeremy@goop.org, Jean Delvare <jdelvare@suse.com>, hpa@zytor.com, peterz@infradead.org, x86@kernel.org, akataria@vmware.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, chrisw@sous-sol.org, mingo@redhat.com, david.vrabel@citrix.com, Douglas_Warzecha@dell.com, pali.rohar@gmail.com, xen-devel@lists.xenproject.org, tglx@linutronix.de, boris.ostrovsky@oracle.com, linux@roeck-us.net
List-Id: virtualization@lists.linuxfoundation.org

On 21/03/16 14:42, Jan Beulich wrote:
>>>> On 21.03.16 at 13:24, <JGross@suse.com> wrote:
>> @@ -758,9 +759,14 @@ struct smp_sync_call_struct {
>>  static void smp_call_sync_callback(struct work_struct *work)
>>  {
>>  	struct smp_sync_call_struct *sscs;
>> +	unsigned int cpu = smp_processor_id();
> 
> So this obtains the vCPU number, yet ...
> 
>>  	sscs = container_of(work, struct smp_sync_call_struct, work);
>> +	preempt_disable();
>> +	hypervisor_pin_vcpu(cpu);
> 
> ... here you're supposed to pass a pCPU number.
> 
> Also don't you need to call smp_processor_id() after preempt_disable()?

No, I'm running on the workqueue bound to the specific (v)cpu and I'm
expecting this vcpu to be pinned to the same numbered pcpu.

preempt_disable() is just called to avoid scheduling of another thread
while the override pinning is active.


Juergen