[PATCH v4 1/6] KVM: s390: pci: Reject adapter interrupt forwarding if already enabled

[Farhan Ali <alifm@linux.ibm.com>]

The MPCIFC instruction doesn't allow registering adapter interrupts without
first unregistering. So reject any request to enable interrupt forwarding
if its already enabled for the zPCI device. This also fixes overwriting and
thus leaking resources when the ioctl is called multiple times for the same
device.

Fixes: 3c5a1b6f0a18 ("KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding")
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
 arch/s390/kvm/pci.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
index 720bb58cabe2..d2a11cdf6941 100644
--- a/arch/s390/kvm/pci.c
+++ b/arch/s390/kvm/pci.c
@@ -237,6 +237,10 @@ static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
 	if (zdev->gisa == 0)
 		return -EINVAL;
 
+	/* AIF already enabled for the device */
+	if (zdev->kzdev->fib.fmt0.aibv != 0)
+		return -EINVAL;
+
 	kvm = zdev->kzdev->kvm;
 	msi_vecs = min_t(unsigned int, fib->fmt0.noi, zdev->max_msi);
 
-- 
2.43.0