Re: [PATCH v8 1/2] x86/kexec: add a new atomic notifier list for kdump

Eric W. Biederman
2012-11-26T15:09:28Z

Zhang Yanfei <zhangyanfei@cn.fujitsu.com> writes:

> This patch adds an atomic notifier list named crash_notifier_list.
> Currently, 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.

crash_notifier_list ick gag please no. Effectively this makes the kexec
on panic code path undebuggable.

Instead we need to use direct function calls to whatever you are doing.

If a direct function call is too complex then the piece of code you want
to call is almost certainly too complex to be calling on a code path
like this.

Eric

> Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
> ---
> arch/x86/include/asm/kexec.h | 2 ++
> arch/x86/kernel/crash.c | 9 +++++++++
> 2 files changed, 11 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..c5b2f70 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 +32,9 @@
>
> int in_crash_kexec;
>
> +ATOMIC_NOTIFIER_HEAD(crash_notifier_list);
> +EXPORT_SYMBOL_GPL(crash_notifier_list);
> +
> #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
>
> static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
> @@ -46,6 +51,8 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
> #endif
> crash_save_cpu(regs, cpu);
>
> + atomic_notifier_call_chain(&crash_notifier_list, 0, NULL);
> +
> /* Disable VMX or SVM if needed.
> *
> * We need to disable virtualization on all CPUs.
> @@ -88,6 +95,8 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
>
> kdump_nmi_shootdown_cpus();
>
> + atomic_notifier_call_chain(&crash_notifier_list, 0, NULL);
> +
> /* Booting kdump kernel with VMX or SVM enabled won't work,
> * because (among other limitations) we can't disable paging
> * with the virt flags.