From: David Hildenbrand david@redhat.com
[ Upstream commit 4d4cee96fb7a3cc53702a9be8299bf525be4ee98 ]
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. the correct thing to do is to return 1 as rc == 1 is the internal representation of "we have to go back into g2".
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@vger.kernel.org # v4.8+ Signed-off-by: David Hildenbrand david@redhat.com Link: https://lore.kernel.org/r/20200403153050.20569-3-david@redhat.com Reviewed-by: Claudio Imbrenda imbrenda@linux.ibm.com Reviewed-by: Christian Borntraeger borntraeger@de.ibm.com [borntraeger@de.ibm.com: fix patch description] Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 a2b28cd1e3fed..17d73b71df1d8 100644 --- a/arch/s390/kvm/vsie.c +++ b/arch/s390/kvm/vsie.c @@ -1024,6 +1024,7 @@ 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; }