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Date: Tue, 7 Apr 2020 13:00:13 +0200 From: Claudio Imbrenda <imbrenda@...ux.ibm.com> To: David Hildenbrand <david@...hat.com> Cc: kvm@...r.kernel.org, linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org, Vasily Gorbik <gor@...ux.ibm.com>, Heiko Carstens <heiko.carstens@...ibm.com>, Cornelia Huck <cohuck@...hat.com>, Janosch Frank <frankja@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ibm.com>, stable@...r.kernel.org Subject: Re: [PATCH v2 2/5] KVM: s390: vsie: Fix delivery of addressing exceptions On Fri, 3 Apr 2020 17:30:47 +0200 David Hildenbrand <david@...hat.com> wrote: > Whenever we get an -EFAULT, we failed to read in guest 2 physical > address space. Such addressing exceptions are reported via a program > intercept to the nested hypervisor. > > We faked the intercept, we have to return to guest 2. Instead, right > now we would be returning -EFAULT from the intercept handler, > eventually crashing the VM. > > Addressing exceptions can only happen if the g2->g3 page tables > reference invalid g2 addresses (say, either a table or the final page > is not accessible - so something that basically never happens in sane > environments. > > Identified by manual code inspection. > > Fixes: a3508fbe9dc6 ("KVM: s390: vsie: initial support for nested > virtualization") Cc: <stable@...r.kernel.org> # v4.8+ > Signed-off-by: David Hildenbrand <david@...hat.com> > --- > arch/s390/kvm/vsie.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c > index 076090f9e666..4f6c22d72072 100644 > --- a/arch/s390/kvm/vsie.c > +++ b/arch/s390/kvm/vsie.c > @@ -1202,6 +1202,7 @@ static int vsie_run(struct kvm_vcpu *vcpu, > struct vsie_page *vsie_page) scb_s->iprcc = PGM_ADDRESSING; > scb_s->pgmilc = 4; > scb_s->gpsw.addr = __rewind_psw(scb_s->gpsw, 4); > + rc = 1; > } > return rc; > } so, the reason why we never noticed this issue before is simply that nobody tried running a misbehaving nested guest? Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
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