Re: [PATCH] KVM: s390: Pass initialized arg even if unused

[Janis Schoetterl-Glausch]

On Thu, 2022-08-25 at 10:30 +0200, Heiko Carstens wrote:
> On Wed, Aug 24, 2022 at 05:30:11PM +0200, Janis Schoetterl-Glausch wrote:
> > This silences smatch warnings reported by kbuild bot:
> > arch/s390/kvm/gaccess.c:859 guest_range_to_gpas() error: uninitialized symbol 'prot'.
> > arch/s390/kvm/gaccess.c:1064 access_guest_with_key() error: uninitialized symbol 'prot'.
> > 
> > This is because it cannot tell that the value is not used in this case.
> > The trans_exc* only examine prot if code is PGM_PROTECTION.
> > Pass a dummy value for other codes.
> > 
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx>
> > ---
> >  arch/s390/kvm/gaccess.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)

[...]

> >  			gpa = kvm_s390_real_to_abs(vcpu, ga);
> > -			if (kvm_is_error_gpa(vcpu->kvm, gpa))
> > +			if (kvm_is_error_gpa(vcpu->kvm, gpa)) {
> >  				rc = PGM_ADDRESSING;
> > +				prot = PROT_NONE;
> > +			}
> ...
> > +		if (rc == PGM_PROTECTION)
> > +			prot = PROT_TYPE_KEYC;
> > +		else
> > +			prot = PROT_NONE;
> 
> For both cases I would suggest to preinitialize prot with PROT_NONE in
> order to keep the code smaller - but not my call.

I chose this to make it really obvious that PROT_NONE is used only in
cases where code != PGM_PROTECTION.