Re: [Qemu-devel] [PATCH] migration: Make analyze-migration script target-page-size aware

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Alexander Graf (agraf@suse.de) wrote:
> 
> 
> On 07.07.17 17:00, Dr. David Alan Gilbert wrote:
> > * Alexander Graf (agraf@suse.de) wrote:
> > > The configuration section has a new subsection to transmit the target page
> > > size along with the migration stream. The analyze migration script needs
> > > to learn about that to read configuration streams that were triggering
> > > this subsection to get transmitted.
> > > 
> > > With this patch applied, I can successfully analyze migration streams
> > > on AArch64 again.
> > > 
> > > Signed-off-by: Alexander Graf <agraf@suse.de>
> > > ---
> > >   scripts/analyze-migration.py | 13 +++++++++++++
> > >   1 file changed, 13 insertions(+)
> > > 
> > > diff --git a/scripts/analyze-migration.py b/scripts/analyze-migration.py
> > > index 1455387..02784f2 100755
> > > --- a/scripts/analyze-migration.py
> > > +++ b/scripts/analyze-migration.py
> > > @@ -254,12 +254,25 @@ class HTABSection(object):
> > 
> > (Note I'm not a particularly python person, so take lightly)
> > 
> > >   class ConfigurationSection(object):
> > > +    QEMU_VM_SUBSECTION    = 0x05
> > > +
> > 
> > It's odd, you already have this constant defined twice in this script.
> 
> Yes, it lives once per class. I am not sure how to easily make it a global.
> 
> > 
> > >       def __init__(self, file):
> > >           self.file = file
> > >       def read(self):
> > >           name_len = self.file.read32()
> > >           name = self.file.readstr(len = name_len)
> > > +        oldpos = self.file.tell()
> > > +        if self.file.read8() == self.QEMU_VM_SUBSECTION:
> > > +            name = self.file.readstr()
> > > +            version_id = self.file.read32()
> > > +            if name == "configuration/target-page-bits":
> > > +                target_page_size = self.file.read32()
> > 
> > All of your other references to target_page_size in the script
> > are self.TARGET_PAGE_SIZE.
> 
> Well, all other ones are actual page sizes :). This variable is never used
> anywhere - we just want to stash it somewhere.

Well you do read self.TARGET_PAGE_SIZE elsewhere - it determines the
amount of data to read from each RAM header in RamSections::read

Also note that the value being read in the config header is
target_page_bits - i.e. ln2(target_page_size).

> > You might want to make the conditional subsection check into a function
> > somewhere, but that's OK for now.
> 
> I really hope we don't need it again. All subsections should be described
> via the in-stream json description. We just missed out the configuration one
> because it's not part of the object model.

Dave

> 
> Alex
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK