Re: [PATCH 2/2] arm/xen: Add misuse warning to virt_to_gfn

[Jürgen Groß <jgross@xxxxxxxx>]

On 27.08.20 10:24, Julien Grall wrote:
> On 27/08/2020 06:21, Jürgen Groß wrote:
> > On 26.08.20 20:37, Julien Grall wrote:
> > "Usually" is a bit gross here. The only generic call site I could find
> > is xenbus_grant_ring(). All other instances (I counted 22) are not
> > generic at all.
> >
> > > will only catch one instance and it means we would have to fix the 
> > > first instance and then re-run to catch the others.
> > > So I think we want to switch to WARN_ON() here.
> > No, please don't. In case there would be a frequent path the result
> > would be a basically unusable system due to massive console clobbering.
> Right, but if that's really happenning then you have a much bigger 
> problem on your platform because the address returned will be invalid.
> So I still don't see the advantage of WARN_ON_ONCE() here.
Depends of the (potential) source of the warnings. I think we can agree
that e.g. a problem in the pv network stack is rather improbable, as it
would have been detected long ago.

If, however, the problem is being introduced by one of the rather new
pv-drivers (like sound, pvcalls, 9pfs) it is perfectly fine to assume
the overall system is still functional even without those drivers
working correctly. Having a message storm from those sources is still
quite undesirable IMO and doesn't really help.


Juergen