On 2012-07-21 09:12, Wen Congyang 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 startint the kernel
> 
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> ---
>  arch/ia64/include/asm/kvm_para.h    |    5 +++++
>  arch/powerpc/include/asm/kvm_para.h |    5 +++++
>  arch/s390/include/asm/kvm_para.h    |    5 +++++
>  arch/x86/include/asm/kvm_para.h     |    7 +++++++
>  arch/x86/kernel/kvm.c               |   14 ++++++++++++++
>  include/linux/kvm_para.h            |   13 +++++++++++++
>  6 files changed, 49 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/kvm_para.h b/arch/ia64/include/asm/kvm_para.h
> index 2019cb9..187c0e2 100644
> --- a/arch/ia64/include/asm/kvm_para.h
> +++ b/arch/ia64/include/asm/kvm_para.h
> @@ -31,6 +31,11 @@ static inline bool kvm_check_and_clear_guest_paused(void)
>  	return false;
>  }
>  
> +static inline unsigned int kvm_arch_pv_features(void)
> +{
> +	return 0;
> +}
> +
>  #endif
>  
>  #endif
> diff --git a/arch/powerpc/include/asm/kvm_para.h b/arch/powerpc/include/asm/kvm_para.h
> index c18916b..be81aac 100644
> --- a/arch/powerpc/include/asm/kvm_para.h
> +++ b/arch/powerpc/include/asm/kvm_para.h
> @@ -211,6 +211,11 @@ static inline bool kvm_check_and_clear_guest_paused(void)
>  	return false;
>  }
>  
> +static inline unsigned int kvm_arch_pv_features(void)
> +{
> +	return 0;
> +}
> +
>  #endif /* __KERNEL__ */
>  
>  #endif /* __POWERPC_KVM_PARA_H__ */
> diff --git a/arch/s390/include/asm/kvm_para.h b/arch/s390/include/asm/kvm_para.h
> index a988329..3d993b7 100644
> --- a/arch/s390/include/asm/kvm_para.h
> +++ b/arch/s390/include/asm/kvm_para.h
> @@ -154,6 +154,11 @@ static inline bool kvm_check_and_clear_guest_paused(void)
>  	return false;
>  }
>  
> +static inline unsigned int kvm_arch_pv_features(void)
> +{
> +	return 0;
> +}
> +
>  #endif
>  
>  #endif /* __S390_KVM_PARA_H */
> diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
> index 63ab166..c8ad86e 100644
> --- a/arch/x86/include/asm/kvm_para.h
> +++ b/arch/x86/include/asm/kvm_para.h
> @@ -89,6 +89,8 @@ struct kvm_vcpu_pv_apf_data {
>  	__u32 enabled;
>  };
>  
> +#define KVM_PV_PORT	(0x505UL)
> +
>  #ifdef __KERNEL__
>  #include <asm/processor.h>
>  
> @@ -221,6 +223,11 @@ static inline void kvm_disable_steal_time(void)
>  }
>  #endif
>  
> +static inline unsigned int kvm_arch_pv_features(void)
> +{
> +	return inl(KVM_PV_PORT);
> +}
> +
>  #endif /* __KERNEL__ */
>  
>  #endif /* _ASM_X86_KVM_PARA_H */
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index e554e5a..9a97f7e 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -328,6 +328,17 @@ 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)
> +{
> +	outl(KVM_PV_PANICKED, KVM_PV_PORT);
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block kvm_pv_panic_nb = {
> +	.notifier_call = kvm_pv_panic_notify,
> +};
> +
>  static u64 kvm_steal_clock(int cpu)
>  {
>  	u64 steal;
> @@ -414,6 +425,9 @@ void __init kvm_guest_init(void)
>  
>  	paravirt_ops_setup();
>  	register_reboot_notifier(&kvm_pv_reboot_nb);
> +	if (kvm_pv_has_feature(KVM_PV_FEATURE_PANICKED))
> +		atomic_notifier_chain_register(&panic_notifier_list,
> +			&kvm_pv_panic_nb);
>  	for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
>  		spin_lock_init(&async_pf_sleepers[i].lock);
>  	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
> diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
> index ff476dd..e73efcf 100644
> --- a/include/linux/kvm_para.h
> +++ b/include/linux/kvm_para.h
> @@ -20,6 +20,12 @@
>  #define KVM_HC_FEATURES			3
>  #define KVM_HC_PPC_MAP_MAGIC_PAGE	4
>  
> +/* The bit of the value read from KVM_PV_PORT */
> +#define KVM_PV_FEATURE_PANICKED	0
> +
> +/* The value writen to KVM_PV_PORT */
> +#define KVM_PV_PANICKED		1
> +
>  /*
>   * hypercalls use architecture specific
>   */
> @@ -33,5 +39,12 @@ 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))

Reading from an invalid I/O port will return -1. So your test will
deliver a wrong result on a platform that doesn't support this PV channel.

Jan

> +		return 1;
> +	return 0;
> +}
>  #endif /* __KERNEL__ */
>  #endif /* __LINUX_KVM_PARA_H */
>