Re: [PATCH v5 1/2] x86/kexec: VMCLEAR vmcss on all cpus if necessary

[Gleb Natapov <gleb-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Wed, Nov 21, 2012 at 10:23:12AM +0800, Zhang Yanfei wrote:
> This patch adds an atomic notifier list named crash_notifier_list.
> When loading kvm-intel module, a notifier will be registered in
> the list to enable vmcss loaded on all cpus to be VMCLEAR'd if
> needed.
> 
> Signed-off-by: Zhang Yanfei <zhangyanfei-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  arch/x86/include/asm/kexec.h |    2 ++
>  arch/x86/kernel/crash.c      |   25 +++++++++++++++++++++++++
>  2 files changed, 27 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
> index 317ff17..5e22b00 100644
> --- a/arch/x86/include/asm/kexec.h
> +++ b/arch/x86/include/asm/kexec.h
> @@ -163,6 +163,8 @@ struct kimage_arch {
>  };
>  #endif
>  
> +extern struct atomic_notifier_head crash_notifier_list;
> +
>  #endif /* __ASSEMBLY__ */
>  
>  #endif /* _ASM_X86_KEXEC_H */
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 13ad899..0f3d5b4 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -16,6 +16,8 @@
>  #include <linux/delay.h>
>  #include <linux/elf.h>
>  #include <linux/elfcore.h>
> +#include <linux/module.h>
> +#include <linux/notifier.h>
>  
>  #include <asm/processor.h>
>  #include <asm/hardirq.h>
> @@ -30,6 +32,19 @@
>  
>  int in_crash_kexec;
>  
> +/*
> + * The list is used to VMCLEAR vmcss loaded on all
> + * cpus. And when loading kvm_intel module, the
> + * vmclear function will be registered in the list.
> + */
> +ATOMIC_NOTIFIER_HEAD(crash_notifier_list);
> +EXPORT_SYMBOL_GPL(crash_notifier_list);
> +
> +static inline void cpu_emergency_vmclear_loaded_vmcss(void)
> +{
> +	atomic_notifier_call_chain(&crash_notifier_list, 0, NULL);
> +}
> +
The notifier list is not VMX specific. It may be used for other
purposes, so please use better name or just open code it.

ACKs from kexec side are needed.

>  #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
>  
>  static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
> @@ -46,6 +61,11 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
>  #endif
>  	crash_save_cpu(regs, cpu);
>  
> +	/*
> +	 * VMCLEAR vmcss loaded on all cpus if needed.
> +	 */
> +	cpu_emergency_vmclear_loaded_vmcss();
> +
>  	/* Disable VMX or SVM if needed.
>  	 *
>  	 * We need to disable virtualization on all CPUs.
> @@ -88,6 +108,11 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
>  
>  	kdump_nmi_shootdown_cpus();
>  
> +	/*
> +	 * VMCLEAR vmcss loaded on this cpu if needed.
> +	 */
> +	cpu_emergency_vmclear_loaded_vmcss();
> +
>  	/* Booting kdump kernel with VMX or SVM enabled won't work,
>  	 * because (among other limitations) we can't disable paging
>  	 * with the virt flags.
> -- 
> 1.7.1
> 
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--
			Gleb.