Re: [Xen-devel] [PATCH 01/11] kexec: add kexec_is_loaded function

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 28 Jul 2011, Olaf Hering wrote:
> Add a new function kexec_is_loaded to be used by subsequent changes for
> kexec in Xen HVM guests with PV drivers loaded.
> 
> A kexec reboot in a HVM guest needs to unregister all resources such as
> xenstore watches and virqs, otherwise the kexec kernel can not bind to
> these resources again. But the unregister only needs to happen during a
> kexec boot because the guest remains the same from the Xen point of
> view. A normal reboot will shutdown and destroy the entire guest with
> all its resources, then the guest will start again with a different
> domain_id number. So doing all the unregister work would only delay
> normal reboots.
> 
> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
> 
> ---
>  include/linux/kexec.h |    3 ++-
>  kernel/kexec.c        |    8 +++++++-
>  kernel/ksysfs.c       |    2 +-
>  3 files changed, 10 insertions(+), 3 deletions(-)
> 
> Index: linux-3.0/include/linux/kexec.h
> ===================================================================
> --- linux-3.0.orig/include/linux/kexec.h
> +++ linux-3.0/include/linux/kexec.h
> @@ -126,6 +126,7 @@ extern asmlinkage long compat_sys_kexec_
>  extern struct page *kimage_alloc_control_pages(struct kimage *image,
>                                               unsigned int order);
>  extern void crash_kexec(struct pt_regs *);
> +extern int kexec_is_loaded(void);
>  int kexec_should_crash(struct task_struct *);
>  void crash_save_cpu(struct pt_regs *regs, int cpu);
>  void crash_save_vmcoreinfo(void);
> @@ -156,7 +157,6 @@ unsigned long paddr_vmcoreinfo_note(void
>  #define VMCOREINFO_CONFIG(name) \
>       vmcoreinfo_append_str("CONFIG_%s=y\n", #name)
>  
> -extern struct kimage *kexec_image;
>  extern struct kimage *kexec_crash_image;
>  
>  #ifndef kexec_flush_icache_page
> @@ -214,6 +214,7 @@ void crash_free_reserved_phys_range(unsi
>  struct pt_regs;
>  struct task_struct;
>  static inline void crash_kexec(struct pt_regs *regs) { }
> +static inline int kexec_is_loaded(void) { return 0; }
>  static inline int kexec_should_crash(struct task_struct *p) { return 0; }
>  #endif /* CONFIG_KEXEC */
>  #endif /* LINUX_KEXEC_H */
> Index: linux-3.0/kernel/kexec.c
> ===================================================================
> --- linux-3.0.orig/kernel/kexec.c
> +++ linux-3.0/kernel/kexec.c
> @@ -934,7 +934,7 @@ static int kimage_load_segment(struct ki
>   * kexec does not sync, or unmount filesystems so if you need
>   * that to happen you need to do that yourself.
>   */
> -struct kimage *kexec_image;
> +static struct kimage *kexec_image;
>  struct kimage *kexec_crash_image;
>  
>  static DEFINE_MUTEX(kexec_mutex);
> @@ -1567,3 +1567,9 @@ int kernel_kexec(void)
>       mutex_unlock(&kexec_mutex);
>       return error;
>  }
> +
> +int kexec_is_loaded(void)
> +{
> +     return !!kexec_image;
> +}
> +EXPORT_SYMBOL_GPL(kexec_is_loaded);

Wouldn't this return true just if a kexec_image is loaded no matter if
this is a normal shutdown or if it is an actually kexec reboot?

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