Re: [PATCH] tools/kvm_stat: Fix kvm_exit filter name

[Gavin Shan <gshan@xxxxxxxxxx>]

On 12/10/19 7:45 PM, Vitaly Kuznetsov wrote:
> Gavin Shan <gshan@xxxxxxxxxx> writes:
>
> > The filter name is fixed to "exit_reason" for some kvm_exit events, no
> > matter what architect we have. Actually, the filter name ("exit_reason")
> > is only applicable to x86, meaning it's broken on other architects
> > including aarch64.
> >
> > This fixes the issue by providing various kvm_exit filter names, depending
> > on architect we're on. Afterwards, the variable filter name is picked and
> > applied through ioctl(fd, SET_FILTER).
>
> Would it actually make sense to standardize (to certain extent) kvm_exit
> tracepoints instead?

Yes, It makes sense, but it's something for future if you agree. Besides,
It seems that other kvm tracepoints need standardization either.

> > Reported-by: Andrew Jones <drjones@xxxxxxxxxx>
> > Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> > ---
> >   tools/kvm/kvm_stat/kvm_stat | 8 ++++++--
> >   1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/kvm/kvm_stat/kvm_stat b/tools/kvm/kvm_stat/kvm_stat
> > index ad1b9e646c49..f9273614b7e3 100755
> > --- a/tools/kvm/kvm_stat/kvm_stat
> > +++ b/tools/kvm/kvm_stat/kvm_stat
> > @@ -270,6 +270,7 @@ class ArchX86(Arch):
> >       def __init__(self, exit_reasons):
> >           self.sc_perf_evt_open = 298
> >           self.ioctl_numbers = IOCTL_NUMBERS
> > +        self.exit_field = 'exit_reason'
>
> Also, 'exit_field' name is confusing (probably because I'm thinking of
> VMCS fields)

Ok. How about to have 'exit_reason_field' or 'exit_filter_name'?

> >           self.exit_reasons = exit_reasons
> >   
> >       def debugfs_is_child(self, field):
> > @@ -289,6 +290,7 @@ class ArchPPC(Arch):
> >           # numbers depend on the wordsize.
> >           char_ptr_size = ctypes.sizeof(ctypes.c_char_p)
> >           self.ioctl_numbers['SET_FILTER'] = 0x80002406 | char_ptr_size << 16
> > +        self.exit_field = 'exit_nr'
> >           self.exit_reasons = {}
> >   
> >       def debugfs_is_child(self, field):
> > @@ -300,6 +302,7 @@ class ArchA64(Arch):
> >       def __init__(self):
> >           self.sc_perf_evt_open = 241
> >           self.ioctl_numbers = IOCTL_NUMBERS
> > +        self.exit_field = 'ret'
>
> And this is the most confusing part. Why do we have 'ret' as an exit
> reason in the first place?

ah, it turns to be 'esr_ec', which is the class code from ESR_EL2. Will fix in v2.
The field name isn't meaningful and it's to be sorted out in future standardization
by the way :)


> >           self.exit_reasons = AARCH64_EXIT_REASONS
> >   
> >       def debugfs_is_child(self, field):
> > @@ -311,6 +314,7 @@ class ArchS390(Arch):
> >       def __init__(self):
> >           self.sc_perf_evt_open = 331
> >           self.ioctl_numbers = IOCTL_NUMBERS
> > +        self.exit_field = None
> >           self.exit_reasons = None
> >   
> >       def debugfs_is_child(self, field):
> > @@ -541,8 +545,8 @@ class TracepointProvider(Provider):
> >           """
> >           filters = {}
> >           filters['kvm_userspace_exit'] = ('reason', USERSPACE_EXIT_REASONS)
> > -        if ARCH.exit_reasons:
> > -            filters['kvm_exit'] = ('exit_reason', ARCH.exit_reasons)
> > +        if ARCH.exit_field and ARCH.exit_reasons:
> > +            filters['kvm_exit'] = (ARCH.exit_field, ARCH.exit_reasons)
> >           return filters
> >   
> >       def _get_available_fields(self):

Regards,
Gavin