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

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Date:	Fri, 26 Apr 2013 17:27:20 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"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 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?


>  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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