linux-kernel - Re: [PATCH v4 2/7] xen/arm: SMP support

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Message-ID: <1366897221.20256.544.camel@zakaz.uk.xensource.com>
Date:	Thu, 25 Apr 2013 14:40:21 +0100
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
CC:	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Subject: Re: [PATCH v4 2/7] xen/arm: SMP support

On Wed, 2013-04-24 at 20:28 +0100, Stefano Stabellini wrote:
> Map vcpu_info using VCPUOP_register_vcpu_info on secondary cpus.
> 
> Call enable_percpu_irq on every cpu.
> 
> Changed in v2:
> - move the percpu variable argument fix to a separate patch;
> - remove unused variable.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> ---
>  arch/arm/xen/enlighten.c |   38 +++++++++++++++++++++++++++++++++++++-
>  1 files changed, 37 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 99ce189..94bbf3b 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -2,6 +2,7 @@
>  #include <xen/events.h>
>  #include <xen/grant_table.h>
>  #include <xen/hvm.h>
> +#include <xen/interface/vcpu.h>
>  #include <xen/interface/xen.h>
>  #include <xen/interface/memory.h>
>  #include <xen/interface/hvm/params.h>
> @@ -32,6 +33,7 @@ struct shared_info xen_dummy_shared_info;
>  struct shared_info *HYPERVISOR_shared_info = (void *)&xen_dummy_shared_info;
>  
>  DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
> +DEFINE_PER_CPU(struct vcpu_info, xen_vcpu_info);

>  /* These are unused until we support booting "pre-ballooned" */
>  unsigned long xen_released_pages;
> @@ -148,6 +150,32 @@ int xen_unmap_domain_mfn_range(struct vm_area_struct *vma,
>  }
>  EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range);
>  
> +static int __init xen_secondary_init(unsigned int cpu)
> +{
> +	struct vcpu_register_vcpu_info info;
> +	struct vcpu_info *vcpup;
> +	int err;
> +
> +	if (cpu == 0)
> +		return 0;
> +
> +	pr_info("Xen: initializing cpu%d\n", cpu);
> +	vcpup = &per_cpu(xen_vcpu_info, cpu);
> +
> +	info.mfn = __pa(vcpup) >> PAGE_SHIFT;
> +	info.offset = offset_in_page(vcpup);

Do you need to somehow guarantee it's not going to cross a page? Maybe
standard C alignment rules make that the case?

> @@ -216,6 +245,8 @@ static int __init xen_guest_init(void)
>  	 * is required to use VCPUOP_register_vcpu_info to place vcpu info
>  	 * for secondary CPUs as they are brought up. */
>  	per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
> +	for_each_online_cpu(i)
> +		xen_secondary_init(i);
>  
>  	gnttab_init();
>  	if (!xen_initial_domain())
[...]
> @@ -244,7 +280,7 @@ static int __init xen_init_events(void)
>  		return -EINVAL;
>  	}
>  
> -	enable_percpu_irq(xen_events_irq, 0);
> +	on_each_cpu(xen_percpu_enable_events, NULL, 0);

It feels like there ought to be some sort of per-cpu bringup callback
which takes care of these dynamically. Maybe that doesn't matter until
we get vcpu hotplug going?

>  
>  	return 0;
>  }


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