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

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Gavin Shan <gshan@redhat.com> 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?

>
> Reported-by: Andrew Jones <drjones@redhat.com>
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  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)

>          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?

>          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):

-- 
Vitaly