Re: [PATCH 2/3] tests/acceptance/machine_s390_ccw_virtio: Test virtio-rng via /dev/hwrng

[Cornelia Huck]

On Sat, 12 Dec 2020 08:10:01 +0100
Thomas Huth <thuth@redhat.com> wrote:

Minor nit: I think that the subject is a bit unwieldy. What about

"tests/acceptance: Test virtio-rng on s390 via /dev/hwrng"

?

> On 11/12/2020 21.30, Wainer dos Santos Moschetta wrote:
> > Hi,
> > 
> > On 12/11/20 2:31 PM, Thomas Huth wrote:  
> >> /dev/hwrng is only functional if virtio-rng is working right, so let's
> >> add a sanity check for this device node.  
> > 
> > Good idea.
> >   
> >>
> >> Signed-off-by: Thomas Huth <thuth@redhat.com>
> >> ---
> >>   tests/acceptance/machine_s390_ccw_virtio.py | 17 +++++++++++++++--
> >>   1 file changed, 15 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/tests/acceptance/machine_s390_ccw_virtio.py
> >> b/tests/acceptance/machine_s390_ccw_virtio.py
> >> index 733a7ca24a..7d0a78139b 100644
> >> --- a/tests/acceptance/machine_s390_ccw_virtio.py
> >> +++ b/tests/acceptance/machine_s390_ccw_virtio.py
> >> @@ -64,9 +64,9 @@ class S390CCWVirtioMachine(Test):
> >>                            '-append', kernel_command_line,
> >>                            '-device', 'virtio-net-ccw,devno=fe.1.1111',
> >>                            '-device',
> >> -                         'virtio-rng-ccw,devno=fe.2.0000,max_revision=0',
> >> +                        
> >> 'virtio-rng-ccw,devno=fe.2.0000,max_revision=0,id=rn1',
> >>                            '-device',
> >> -                         'virtio-rng-ccw,devno=fe.3.1234,max_revision=2',
> >> +                        
> >> 'virtio-rng-ccw,devno=fe.3.1234,max_revision=2,id=rn2',
> >>                            '-device', 'zpci,uid=5,target=zzz',
> >>                            '-device', 'virtio-net-pci,id=zzz',
> >>                            '-device', 'zpci,uid=0xa,fid=12,target=serial',
> >> @@ -96,6 +96,19 @@ class S390CCWVirtioMachine(Test):
> >>           exec_command_and_wait_for_pattern(self,
> >>                           'cat
> >> /sys/bus/ccw/devices/0.3.1234/virtio?/features',
> >>                           virtio_rng_features)
> >> +        # check that /dev/hwrng works - and that it's gone after ejecting
> >> +        exec_command_and_wait_for_pattern(self,
> >> +                        'dd if=/dev/hwrng of=/tmp/out.dat bs=1k count=10',
> >> +                        '10+0 records out')
> >> +        self.clear_guests_dmesg()
> >> +        self.vm.command('device_del', id='rn1')
> >> +        self.wait_for_crw_reports()
> >> +        self.clear_guests_dmesg()
> >> +        self.vm.command('device_del', id='rn2')
> >> +        self.wait_for_crw_reports()
> >> +        exec_command_and_wait_for_pattern(self,
> >> +                        'dd if=/dev/hwrng of=/tmp/out.dat bs=1k count=10',

Does this work if you direct the output to /dev/null?

> >> +                        'dd: /dev/hwrng: No such device')  
> > 
> > Maybe the expected pattern is too fragile. On my Fedora 33 system, 'dd' will
> > print a different message.  
> 
> We are running this test with a well-defined kernel + initrd, so I don't
> think we have to care of other versions of dd here.
> 
> > What if it checks for the presence of the device file, e.g:
> > 
> > ... self, 'test -c /dev/hwrng; echo $?', '1')  
> 
> That doesn't work, the /dev/hwrng is still there (so test -c succeeds),
> since this initrd uses static device nodes for this in /dev. /dev/hwrng just
> can not be opened anymore after the device has been removed.

I had been thinking about a different approach to check that, but dd
really looks like the easiest way.