Re: [Xen-devel] [PATCH 12/24] xen/arm: Introduce xen_guest_init

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-07-26 at 16:33 +0100, Stefano Stabellini wrote:
> We used to rely on a core_initcall to initialize Xen on ARM, however
> core_initcalls are actually called after early consoles are initialized.
> That means that hvc_xen.c is going to be initialized before Xen.
> 
> Given the lack of a better alternative, just call a new Xen
> initialization function (xen_guest_init) from xen_cons_init.

Can't we just arrange for this to be called super early on from
setup_arch? That's got to be better than calling it from some random
function which happens to get called early enough.

I presume that KVM is going to want some similarly early init hooks etc
and therefore ARM could benefit from the same sort of infrastructure as
is in arch/x86/include/asm/hypervisor.h?


> 
> xen_guest_init has to be arch independent, so write both an ARM and an
> x86 implementation. The x86 implementation is currently empty because we
> can be sure that xen_hvm_guest_init is called early enough.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> ---
>  arch/arm/xen/enlighten.c  |    7 ++++++-
>  arch/x86/xen/enlighten.c  |    8 ++++++++
>  drivers/tty/hvc/hvc_xen.c |    7 ++++++-
>  include/xen/xen.h         |    2 ++
>  4 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 8c923af..dc68074 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -44,7 +44,7 @@ EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
>   * - one interrupt for Xen event notifications;
>   * - one memory region to map the grant_table.
>   */
> -static int __init xen_guest_init(void)
> +int __init xen_guest_init(void)
>  {
>       int cpu;
>       struct xen_add_to_physmap xatp;
> @@ -58,6 +58,10 @@ static int __init xen_guest_init(void)
>       }
>       xen_domain_type = XEN_HVM_DOMAIN;
>  
> +     /* already setup */
> +     if (shared_info_page != 0 && HYPERVISOR_shared_info == shared_info_page)
> +             return 0;
> +
>       if (!shared_info_page)
>               shared_info_page = (struct shared_info *)
>                       get_zeroed_page(GFP_KERNEL);
> @@ -88,4 +92,5 @@ static int __init xen_guest_init(void)
>       }
>       return 0;
>  }
> +EXPORT_SYMBOL_GPL(xen_guest_init);
>  core_initcall(xen_guest_init);
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index ff962d4..6131d43 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1567,4 +1567,12 @@ const struct hypervisor_x86 x86_hyper_xen_hvm 
> __refconst = {
>       .init_platform          = xen_hvm_guest_init,
>  };
>  EXPORT_SYMBOL(x86_hyper_xen_hvm);
> +
> +int __init xen_guest_init(void)
> +{
> +     /* do nothing: rely on x86_hyper_xen_hvm for the initialization */
> +     return 0;
> +     
> +}
> +EXPORT_SYMBOL_GPL(xen_guest_init);
>  #endif
> diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> index dc07f56..3c04fb8 100644
> --- a/drivers/tty/hvc/hvc_xen.c
> +++ b/drivers/tty/hvc/hvc_xen.c
> @@ -577,6 +577,12 @@ static void __exit xen_hvc_fini(void)
>  static int xen_cons_init(void)
>  {
>       const struct hv_ops *ops;
> +     int r;
> +
> +     /* retrieve xen infos  */
> +     r = xen_guest_init();
> +     if (r < 0)
> +             return r;
>  
>       if (!xen_domain())
>               return 0;
> @@ -584,7 +590,6 @@ static int xen_cons_init(void)
>       if (xen_initial_domain())
>               ops = &dom0_hvc_ops;
>       else {
> -             int r;
>               ops = &domU_hvc_ops;
>  
>               if (xen_hvm_domain())
> diff --git a/include/xen/xen.h b/include/xen/xen.h
> index 2c0d3a5..792a4d2 100644
> --- a/include/xen/xen.h
> +++ b/include/xen/xen.h
> @@ -9,8 +9,10 @@ enum xen_domain_type {
>  
>  #ifdef CONFIG_XEN
>  extern enum xen_domain_type xen_domain_type;
> +int xen_guest_init(void);
>  #else
>  #define xen_domain_type              XEN_NATIVE
> +static inline int xen_guest_init(void) { return 0; }
>  #endif
>  
>  #define xen_domain()         (xen_domain_type != XEN_NATIVE)



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