linux-kernel - Re: [PATCH 8/9] xen/smp/pvhvm: Don't initialize IRQ

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Date:	Mon, 29 Apr 2013 14:34:04 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [PATCH 8/9] xen/smp/pvhvm: Don't initialize IRQ_WORKER as we are
 using the native one.

On Fri, Apr 26, 2013 at 05:27:20PM +0100, Stefano Stabellini wrote:
> On Tue, 16 Apr 2013, Konrad Rzeszutek Wilk wrote:
> > There is no need to use the PV version of the IRQ_WORKER mechanism
> > as under PVHVM we are using the native version. The native
> > version is using the SMP API.
> > 
> > They just sit around unused:
> > 
> >   69:          0          0  xen-percpu-ipi       irqwork0
> >   83:          0          0  xen-percpu-ipi       irqwork1
> > 
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> 
> Might be worth trying to make it work instead?
> Is it just because we don't set the apic->send_IPI_* functions to the
> xen specific version on PVHVM?
> 

Right. We use the baremetal mechanism to do it. And it works fine.

> 
> >  arch/x86/xen/smp.c | 13 ++++++++++++-
> >  1 file changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> > index 22c800a..415694c 100644
> > --- a/arch/x86/xen/smp.c
> > +++ b/arch/x86/xen/smp.c
> > @@ -144,6 +144,13 @@ static int xen_smp_intr_init(unsigned int cpu)
> >  		goto fail;
> >  	per_cpu(xen_callfuncsingle_irq, cpu) = rc;
> >  
> > +	/*
> > +	 * The IRQ worker on PVHVM goes through the native path and uses the
> > +	 * IPI mechanism.
> > +	 */
> > +	if (xen_hvm_domain())
> > +		return 0;
> > +
> >  	callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
> >  	rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
> >  				    cpu,
> > @@ -167,6 +174,9 @@ static int xen_smp_intr_init(unsigned int cpu)
> >  	if (per_cpu(xen_callfuncsingle_irq, cpu) >= 0)
> >  		unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu),
> >  				       NULL);
> > +	if (xen_hvm_domain())
> > +		return rc;
> > +
> >  	if (per_cpu(xen_irq_work, cpu) >= 0)
> >  		unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
> >  
> > @@ -661,7 +671,8 @@ static void xen_hvm_cpu_die(unsigned int cpu)
> >  	unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
> >  	unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
> >  	unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
> > -	unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
> > +	if (!xen_hvm_domain())
> > +		unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
> >  	xen_uninit_lock_cpu(cpu);
> >  	xen_teardown_timer(cpu);
> >  	native_cpu_die(cpu);
> > -- 
> > 1.8.1.4
> > 
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