Re: [Qemu-devel] [PATCH v12 rebased] kvm: notify host when the guest is panicked

[Marcelo Tosatti]

Hi,

On Wed, Jan 23, 2013 at 03:19:21PM +0800, Hu Tao wrote:
> We can know the guest is panicked when the guest runs on xen.
> But we do not have such feature on kvm.
> 
> Another purpose of this feature is: management app(for example:
> libvirt) can do auto dump when the guest is panicked. If management
> app does not do auto dump, the guest's user can do dump by hand if
> he sees the guest is panicked.
> 
> We have three solutions to implement this feature:
> 1. use vmcall
> 2. use I/O port
> 3. use virtio-serial.
> 
> We have decided to avoid touching hypervisor. The reason why I choose
> choose the I/O port is:
> 1. it is easier to implememt
> 2. it does not depend any virtual device
> 3. it can work when starting the kernel
> 
> Signed-off-by: Wen Congyang <address@hidden>
> Signed-off-by: Hu Tao <address@hidden>
> ---
>  arch/ia64/kvm/irq.h                  | 19 +++++++++++++
>  arch/powerpc/include/asm/kvm_para.h  | 18 ++++++++++++
>  arch/s390/include/asm/kvm_para.h     | 19 +++++++++++++
>  arch/x86/include/asm/kvm_para.h      | 20 ++++++++++++++
>  arch/x86/include/uapi/asm/kvm_para.h |  2 ++
>  arch/x86/kernel/kvm.c                | 53 
> ++++++++++++++++++++++++++++++++++++
>  include/linux/kvm_para.h             | 18 ++++++++++++
>  include/uapi/linux/kvm_para.h        |  6 ++++
>  kernel/panic.c                       |  4 +++
>  9 files changed, 159 insertions(+)
> 
> diff --git a/arch/ia64/kvm/irq.h b/arch/ia64/kvm/irq.h
> index c0785a7..b3870f8 100644
> --- a/arch/ia64/kvm/irq.h
> +++ b/arch/ia64/kvm/irq.h
> @@ -30,4 +30,23 @@ static inline int irqchip_in_kernel(struct kvm *kvm)
>       return 1;
>  }
>  
> +static inline int kvm_arch_pv_event_init(void)
> +{
> +     return 0;
> +}
> +
> +static inline unsigned int kvm_arch_pv_features(void)
> +{
> +     return 0;
> +}
> +
> +static inline void kvm_arch_pv_eject_event(unsigned int event)
> +{
> +}
> +
> +static inline bool kvm_arch_pv_event_enabled(void)
> +{
> +     return false;
> +}
> +

The interface is x86 only, no need to touch other architectures.

>  #endif
> diff --git a/arch/powerpc/include/asm/kvm_para.h 
> b/arch/powerpc/include/asm/kvm_para.h
> index 2b11965..17dd013 100644
> --- a/arch/powerpc/include/asm/kvm_para.h
> +++ b/arch/powerpc/include/asm/kvm_para.h
> @@ -144,4 +144,22 @@ static inline bool kvm_check_and_clear_guest_paused(void)
>       return false;
>  }
>  
> +static inline int kvm_arch_pv_event_init(void)
> +{
> +     return 0;
> +}
> +
> +static inline unsigned int kvm_arch_pv_features(void)
> +{
> +     return 0;
> +}
> +
> +static inline void kvm_arch_pv_eject_event(unsigned int event)
> +{
> +}
> +
> +static inline bool kvm_arch_pv_event_enabled(void)
> +{
> +     return false;
> +}
>  #endif /* __POWERPC_KVM_PARA_H__ */
> diff --git a/arch/s390/include/asm/kvm_para.h 
> b/arch/s390/include/asm/kvm_para.h
> index e0f8423..81d87ec 100644
> --- a/arch/s390/include/asm/kvm_para.h
> +++ b/arch/s390/include/asm/kvm_para.h
> @@ -154,4 +154,23 @@ static inline bool kvm_check_and_clear_guest_paused(void)
>       return false;
>  }
>  
> +static inline int kvm_arch_pv_event_init(void)
> +{
> +     return 0;
> +}
> +
> +static inline unsigned int kvm_arch_pv_features(void)
> +{
> +     return 0;
> +}
> +
> +static inline void kvm_arch_pv_eject_event(unsigned int event)
> +{
> +}
> +
> +static inline bool kvm_arch_pv_event_enabled(void)
> +{
> +     return false;
> +}
> +
>  #endif /* __S390_KVM_PARA_H */
> --- a/arch/x86/include/asm/kvm_para.h
> +++ b/arch/x86/include/asm/kvm_para.h
> @@ -133,4 +133,24 @@ static inline void kvm_disable_steal_time(void)
>  }
>  #endif
>  
> +static inline int kvm_arch_pv_event_init(void)
> +{
> +     if (!request_region(KVM_PV_EVENT_PORT, 4, "KVM_PV_EVENT"))
> +             return -1;
> +
> +     return 0;
> +}

This should be in a driver in arch/x86/kernel/kvm-panic.c, or so.

> +
> +static inline unsigned int kvm_arch_pv_features(void)
> +{
> +     return inl(KVM_PV_EVENT_PORT);
> +}
> +
> +static inline void kvm_arch_pv_eject_event(unsigned int event)
> +{
> +     outl(event, KVM_PV_EVENT_PORT);
> +}

> +
> +bool kvm_arch_pv_event_enabled(void);
> +
>  #endif /* _ASM_X86_KVM_PARA_H */
> diff --git a/arch/x86/include/uapi/asm/kvm_para.h 
> b/arch/x86/include/uapi/asm/kvm_para.h
> index 06fdbd9..c15ef33 100644
> --- a/arch/x86/include/uapi/asm/kvm_para.h
> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> @@ -96,5 +96,7 @@ struct kvm_vcpu_pv_apf_data {
>  #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK
>  #define KVM_PV_EOI_DISABLED 0x0
>  
> +#define KVM_PV_EVENT_PORT    (0x505UL)
> +

No need for the ioport to be hard coded. What are the options to
communicate an address to the guest? An MSR, via ACPI?

>  
>  #endif /* _UAPI_ASM_X86_KVM_PARA_H */
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 9c2bd8b..0aa7b3e 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -73,6 +73,20 @@ static int parse_no_kvmclock_vsyscall(char *arg)
>  
>  early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
>  
> +static int pv_event = 1;
> +static int parse_no_pv_event(char *arg)
> +{
> +     pv_event = 0;
> +     return 0;
> +}
> +
> +bool kvm_arch_pv_event_enabled(void)
> +{
> +     return !!pv_event;
> +}
> +
> +early_param("no-pv-event", parse_no_pv_event);
> +

"pv-event" is a bad name for an interface which is specific to notify
panic events. Please use pv-panic everywhere.

>  static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
>  static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
>  static int has_steal_clock = 0;
> @@ -385,6 +399,17 @@ static struct notifier_block kvm_pv_reboot_nb = {
>       .notifier_call = kvm_pv_reboot_notify,
>  };
>  
> +static int
> +kvm_pv_panic_notify(struct notifier_block *nb, unsigned long code, void 
> *unused)
> +{
> +     kvm_pv_eject_event(KVM_PV_EVENT_PANICKED);
> +     return NOTIFY_DONE;
> +}

Why 'eject' ?

> +
> +static struct notifier_block kvm_pv_panic_nb = {
> +     .notifier_call = kvm_pv_panic_notify,
> +};
> +
>  static u64 kvm_steal_clock(int cpu)
>  {
>       u64 steal;
> @@ -462,6 +487,34 @@ static void __init kvm_apf_trap_init(void)
>       set_intr_gate(14, &async_page_fault);
>  }
>  
> +static void __init kvm_pv_panicked_event_init(void)
> +{
> +     if (!kvm_para_available())
> +             return;
> +
> +     if (kvm_pv_has_feature(KVM_PV_FEATURE_PANICKED))
> +             atomic_notifier_chain_register(&panic_notifier_list,
> +                     &kvm_pv_panic_nb);
> +}
> +
> +static inline int kvm_pv_event_init(void)
> +{
> +     return kvm_arch_pv_event_init();
> +}
> +
> +static int __init enable_pv_event(void)
> +{
> +     if (pv_event) {
> +             if (kvm_pv_event_init())
> +                     return 0;
> +
> +             kvm_pv_panicked_event_init();
> +     }
> +
> +     return 0;
> +}
> +arch_initcall(enable_pv_event);

Call the initialization code from kvm_guest_init, only one function is
necessary.

> +
>  void __init kvm_guest_init(void)
>  {
>       int i;
> diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
> index 00a97bb..6fb6198 100644
> --- a/include/linux/kvm_para.h
> +++ b/include/linux/kvm_para.h
> @@ -10,4 +10,22 @@ static inline int kvm_para_has_feature(unsigned int 
> feature)
>               return 1;
>       return 0;
>  }
> +
> +static inline int kvm_pv_has_feature(unsigned int feature)
> +{
> +     if (kvm_arch_pv_features() & (1UL << feature))
> +             return 1;
> +     return 0;
> +}
> +
> +static inline void kvm_pv_eject_event(unsigned int event)
> +{
> +     kvm_arch_pv_eject_event(event);
> +}
> +
> +static inline bool kvm_pv_event_enabled(void)
> +{
> +     return kvm_arch_pv_event_enabled();
> +}

No need for this helpers, as noted.

>  #endif /* __LINUX_KVM_PARA_H */
> diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
> index cea2c5c..c41ddce 100644
> --- a/include/uapi/linux/kvm_para.h
> +++ b/include/uapi/linux/kvm_para.h
> @@ -20,6 +20,12 @@
>  #define KVM_HC_FEATURES                      3
>  #define KVM_HC_PPC_MAP_MAGIC_PAGE    4
>  
> +/* The bit of supported pv event */
> +#define KVM_PV_FEATURE_PANICKED      0
> +
> +/* The pv event value */
> +#define KVM_PV_EVENT_PANICKED        1
> +

This is a hypercall header. You want

arch/x86/include/asm/kvm_para.h

>  /*
>   * hypercalls use architecture specific
>   */
> diff --git a/kernel/panic.c b/kernel/panic.c
> index e1b2822..a764d2e 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -23,6 +23,7 @@
>  #include <linux/init.h>
>  #include <linux/nmi.h>
>  #include <linux/dmi.h>
> +#include <linux/kvm_para.h>
>  
>  #define PANIC_TIMER_STEP 100
>  #define PANIC_BLINK_SPD 18
> @@ -132,6 +133,9 @@ void panic(const char *fmt, ...)
>       if (!panic_blink)
>               panic_blink = no_blink;
>  
> +     if (kvm_pv_event_enabled())
> +             panic_timeout = 0;
> +

What is the rationale behind this?