Re: [PATCH] trace "exit to userspace" event

[Marcelo Tosatti <mtosatti@redhat.com>]

On Tue, Oct 05, 2010 at 03:14:32PM +0200, Gleb Natapov wrote:
> Add tracepoint for userspace exit.
> 
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
> index 6dd3a51..fb44da0 100644
> --- a/include/trace/events/kvm.h
> +++ b/include/trace/events/kvm.h
> @@ -6,6 +6,31 @@
>  #undef TRACE_SYSTEM
>  #define TRACE_SYSTEM kvm
>  
> +#define ERSN(x) { KVM_EXIT_##x, "KVM_EXIT_" #x }
> +
> +#define kvm_trace_exit_reason						\
> +	ERSN(UNKNOWN), ERSN(EXCEPTION), ERSN(IO), ERSN(HYPERCALL),	\
> +	ERSN(DEBUG), ERSN(HLT), ERSN(MMIO), ERSN(IRQ_WINDOW_OPEN),	\
> +	ERSN(SHUTDOWN), ERSN(FAIL_ENTRY), ERSN(INTR), ERSN(SET_TPR),	\
> +	ERSN(TPR_ACCESS), ERSN(S390_SIEIC), ERSN(S390_RESET), ERSN(DCR),\
> +	ERSN(NMI), ERSN(INTERNAL_ERROR), ERSN(OSI)
> +
> +TRACE_EVENT(kvm_userspace_exit,
> +	    TP_PROTO(__u32 reason),
> +	    TP_ARGS(reason),
> +
> +	TP_STRUCT__entry(
> +		__field(	__u32,		reason		)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->reason		= reason;
> +	),
> +
> +	TP_printk("reason %s", __print_symbolic(__entry->reason,
> +						kvm_trace_exit_reason))
> +);
> +
>  #if defined(__KVM_HAVE_IOAPIC)
>  TRACE_EVENT(kvm_set_irq,
>  	TP_PROTO(unsigned int gsi, int level, int irq_source_id),
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index b8499f5..8800713 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1458,6 +1458,8 @@ static long kvm_vcpu_ioctl(struct file *filp,
>  		if (arg)
>  			goto out;
>  		r = kvm_arch_vcpu_ioctl_run(vcpu, vcpu->run);
> +		if (r >= 0)
> +			trace_kvm_userspace_exit(vcpu->run->exit_reason);
>  		break;
>  	case KVM_GET_REGS: {
>  		struct kvm_regs *kvm_regs;
> --
> 			Gleb.

Exit codes are also valid for r == -EINTR and -EAGAIN cases, eg
EXIT_INTR. Better print it out for all cases, and let the reader
decide whether exit_reason is valid.