linux-kernel - Re: [PATCH 7/9] xen/spinlock: Disable IRQ spinlock (PV) allocation on PVHVM

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Message-ID: <alpine.DEB.2.02.1304261718420.4180@kaball.uk.xensource.com>
Date:	Fri, 26 Apr 2013 17:20:23 +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 7/9] xen/spinlock: Disable IRQ spinlock (PV) allocation
 on PVHVM

On Tue, 16 Apr 2013, Konrad Rzeszutek Wilk wrote:
> See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
> (xen: disable PV spinlocks on HVM) for details.
> 
> But we did not disable it everywhere - which means that when
> we boot as PVHVM we end up allocating per-CPU irq line for
> spinlock. This fixes that.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Is there any point in calling xen_init_lock_cpu in PVHVM guests?
At that point we might as well remove the call from xen_hvm_cpu_notify.


>  arch/x86/xen/spinlock.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
> index 47ae032..8b54603 100644
> --- a/arch/x86/xen/spinlock.c
> +++ b/arch/x86/xen/spinlock.c
> @@ -367,6 +367,13 @@ void __cpuinit xen_init_lock_cpu(int cpu)
>  	WARN(per_cpu(lock_kicker_irq, cpu) > 0, "spinlock on CPU%d exists on IRQ%d!\n",
>  	     cpu, per_cpu(lock_kicker_irq, cpu));
>  
> +	/*
> +	 * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
> +	 * (xen: disable PV spinlocks on HVM)
> +	 */
> +	if (xen_hvm_domain())
> +		return;
> +
>  	name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
>  	irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
>  				     cpu,
> @@ -385,12 +392,26 @@ void __cpuinit xen_init_lock_cpu(int cpu)
>  
>  void xen_uninit_lock_cpu(int cpu)
>  {
> +	/*
> +	 * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
> +	 * (xen: disable PV spinlocks on HVM)
> +	 */
> +	if (xen_hvm_domain())
> +		return;
> +
>  	unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
>  	per_cpu(lock_kicker_irq, cpu) = -1;
>  }
>  
>  void __init xen_init_spinlocks(void)
>  {
> +	/*
> +	 * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23
> +	 * (xen: disable PV spinlocks on HVM)
> +	 */
> +	if (xen_hvm_domain())
> +		return;
> +
>  	BUILD_BUG_ON(sizeof(struct xen_spinlock) > sizeof(arch_spinlock_t));
>  
>  	pv_lock_ops.spin_is_locked = xen_spin_is_locked;
> -- 
> 1.8.1.4
> 
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