linux-kernel - Re: [PATCH 07/24] xen/arm: Xen detection and shared

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Date:	Wed, 1 Aug 2012 10:19:59 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	Ian.Campbell@...rix.com, tim@....org,
	linux-arm-kernel@...ts.infradead.org, linaro-dev@...ts.linaro.org,
	catalin.marinas@....com, arnd@...db.de
Subject: Re: [PATCH 07/24] xen/arm: Xen detection and shared_info page mapping

On Thu, Jul 26, 2012 at 04:33:49PM +0100, Stefano Stabellini wrote:
> Check for a "/xen" node in the device tree, if it is present set
> xen_domain_type to XEN_HVM_DOMAIN and continue initialization.
> 
> Map the real shared info page using XENMEM_add_to_physmap with
> XENMAPSPACE_shared_info.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> ---
>  arch/arm/xen/enlighten.c |   56 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 56 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index d27c2a6..8c923af 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -5,6 +5,9 @@
>  #include <asm/xen/hypervisor.h>
>  #include <asm/xen/hypercall.h>
>  #include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_address.h>
>  
>  struct start_info _xen_start_info;
>  struct start_info *xen_start_info = &_xen_start_info;
> @@ -33,3 +36,56 @@ int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
>  	return -ENOSYS;
>  }
>  EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
> +
> +/*
> + * == Xen Device Tree format ==
> + * - /xen node;
> + * - compatible "arm,xen";
> + * - one interrupt for Xen event notifications;
> + * - one memory region to map the grant_table.
> + */
> +static int __init xen_guest_init(void)
> +{
> +	int cpu;
> +	struct xen_add_to_physmap xatp;
> +	static struct shared_info *shared_info_page = 0;
> +	struct device_node *node;
> +
> +	node = of_find_compatible_node(NULL, NULL, "arm,xen");
> +	if (!node) {
> +		pr_info("No Xen support\n");

I don't think the pr_info is appropiate here?
> +		return 0;

Should this be -ENODEV?

> +	}
> +	xen_domain_type = XEN_HVM_DOMAIN;
> +
> +	if (!shared_info_page)
> +		shared_info_page = (struct shared_info *)
> +			get_zeroed_page(GFP_KERNEL);
> +	if (!shared_info_page) {
> +		pr_err("not enough memory");

\n

> +		return -ENOMEM;
> +	}
> +	xatp.domid = DOMID_SELF;
> +	xatp.idx = 0;
> +	xatp.space = XENMAPSPACE_shared_info;
> +	xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
> +	if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
> +		BUG();
> +
> +	HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
> +
> +	/* xen_vcpu is a pointer to the vcpu_info struct in the shared_info
> +	 * page, we use it in the event channel upcall and in some pvclock
> +	 * related functions. We don't need the vcpu_info placement
> +	 * optimizations because we don't use any pv_mmu or pv_irq op on
> +	 * HVM.
> +	 * When xen_hvm_init_shared_info is run at boot time only vcpu 0 is
> +	 * online but xen_hvm_init_shared_info is run at resume time too and
> +	 * in that case multiple vcpus might be online. */
> +	for_each_online_cpu(cpu) {
> +		per_cpu(xen_vcpu, cpu) =
> +			&HYPERVISOR_shared_info->vcpu_info[cpu];
> +	}
> +	return 0;

This above looks stringly similar to the x86 one. Could it be
abstracted away to share the same code? Or is that something that
ought to be done later on when there is more meat on the bone?


> +}
> +core_initcall(xen_guest_init);
> -- 
> 1.7.2.5
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