[PATCH] KVM: s390: pci: Fix aisb calculation

[Matthew Rosato]

The current implementation of aisb calculation will erroneously index
via an unsigned long * as well as multiply by 8B for every 64-bits in
the offset; only one or the other is required.  This throws off aisb
calculations once the number of devices exceeds 64, and can result
in out-of-bounds access as well as failure to indicate summary bits
associated with those devices in guests.

Fix this by converting to a physical address before applying the
offset, as is already done in arch/s390/pci/pci_irq.c.

Fixes: 3c5a1b6f0a18 ("KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding")
Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
---
 arch/s390/kvm/pci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
index 86d93e8dddae..338171f9371b 100644
--- a/arch/s390/kvm/pci.c
+++ b/arch/s390/kvm/pci.c
@@ -166,7 +166,7 @@ static int kvm_zpci_set_airq(struct zpci_dev *zdev)
 	fib.fmt0.noi = airq_iv_end(zdev->aibv);
 	fib.fmt0.aibv = virt_to_phys(zdev->aibv->vector);
 	fib.fmt0.aibvo = 0;
-	fib.fmt0.aisb = virt_to_phys(aift->sbv->vector + (zdev->aisb / 64) * 8);
+	fib.fmt0.aisb = virt_to_phys(aift->sbv->vector) + (zdev->aisb / 64) * 8;
 	fib.fmt0.aisbo = zdev->aisb & 63;
 	fib.gd = zdev->gisa;
 
@@ -309,7 +309,7 @@ static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
 
 	/* Update guest FIB for re-issue */
 	fib->fmt0.aisbo = zdev->aisb & 63;
-	fib->fmt0.aisb = virt_to_phys(aift->sbv->vector + (zdev->aisb / 64) * 8);
+	fib->fmt0.aisb = virt_to_phys(aift->sbv->vector) + (zdev->aisb / 64) * 8;
 	fib->fmt0.isc = gisc;
 
 	/* Save some guest fib values in the host for later use */
-- 
2.53.0