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

[Gleb Natapov <gleb@redhat.com>]

On Thu, Oct 07, 2010 at 01:18:39PM -0300, Marcelo Tosatti wrote:
> 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.
Are they? I see that userspace does not look into run->exit_reason in
case of -EINTR and -EAGAIN.

--
			Gleb.