[PATCH v2 2/5] KVM: s390: vsie: Fix delivery of addressing exceptions

From: David Hildenbrand <david@redhat.com>
To: kvm@vger.kernel.org
Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	Vasily Gorbik <gor@linux.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Janosch Frank <frankja@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	David Hildenbrand <david@redhat.com>,
	stable@vger.kernel.org
Subject: [PATCH v2 2/5] KVM: s390: vsie: Fix delivery of addressing exceptions
Date: Fri,  3 Apr 2020 17:30:47 +0200	[thread overview]
Message-ID: <20200403153050.20569-3-david@redhat.com> (raw)
In-Reply-To: <20200403153050.20569-1-david@redhat.com>

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@vger.kernel.org> # v4.8+
Signed-off-by: David Hildenbrand <david@redhat.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;
 }
-- 
2.25.1

