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Date: Thu, 25 Aug 2022 10:30:25 +0200 From: Heiko Carstens <hca@...ux.ibm.com> To: Janis Schoetterl-Glausch <scgl@...ux.ibm.com> Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Alexander Gordeev <agordeev@...ux.ibm.com>, kernel test robot <lkp@...el.com>, Dan Carpenter <dan.carpenter@...cle.com>, David Hildenbrand <david@...hat.com>, Sven Schnelle <svens@...ux.ibm.com>, kvm@...r.kernel.org, linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] KVM: s390: Pass initialized arg even if unused 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@...el.com> > Reported-by: Dan Carpenter <dan.carpenter@...cle.com> > Signed-off-by: Janis Schoetterl-Glausch <scgl@...ux.ibm.com> > --- > arch/s390/kvm/gaccess.c | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) ... > @@ -503,6 +505,7 @@ static int trans_exc_ending(struct kvm_vcpu *vcpu, int code, unsigned long gva, > > switch (code) { > case PGM_PROTECTION: > + WARN(unlikely(prot == PROT_NONE), "Invalid prot argument"); The WARN macro comes with unlikely, please get rid of unlikely here. Also: > + case PROT_NONE: > + /* We should never get here, acts like termination */ Why not put it here? And make it WARN_ON_ONCE() in addition? > 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.
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