[PATCH v2 3/3] s390x/pci: drive ISM reset from subsystem reset

[Matthew Rosato]

ISM devices are sensitive to manipulation of the IOMMU, so the ISM device
needs to be reset before the vfio-pci device is reset (triggering a full
UNMAP).  In order to ensure this occurs, trigger ISM device resets from
subsystem_reset before triggering the PCI bus reset (which will also
trigger vfio-pci reset).  This only needs to be done for ISM devices
which were enabled for use by the guest.
Further, ensure that AIF is disabled as part of the reset event.

Fixes: ef1535901a ("s390x: do a subsystem reset before the unprotect on reboot")
Fixes: 03451953c7 ("s390x/pci: reset ISM passthrough devices on shutdown and 
system reset")
Reported-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 hw/s390x/s390-pci-bus.c         | 26 +++++++++++++++++---------
 hw/s390x/s390-virtio-ccw.c      |  8 ++++++++
 include/hw/s390x/s390-pci-bus.h |  1 +
 3 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index 347580ebac..3e57d5faca 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -151,20 +151,12 @@ static void s390_pci_shutdown_notifier(Notifier *n, void 
*opaque)
     pci_device_reset(pbdev->pdev);
 }
 
-static void s390_pci_reset_cb(void *opaque)
-{
-    S390PCIBusDevice *pbdev = opaque;
-
-    pci_device_reset(pbdev->pdev);
-}
-
 static void s390_pci_perform_unplug(S390PCIBusDevice *pbdev)
 {
     HotplugHandler *hotplug_ctrl;
 
     if (pbdev->pft == ZPCI_PFT_ISM) {
         notifier_remove(&pbdev->shutdown_notifier);
-        qemu_unregister_reset(s390_pci_reset_cb, pbdev);
     }
 
     /* Unplug the PCI device */
@@ -1132,7 +1124,6 @@ static void s390_pcihost_plug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
             if (pbdev->pft == ZPCI_PFT_ISM) {
                 pbdev->shutdown_notifier.notify = s390_pci_shutdown_notifier;
                 qemu_register_shutdown_notifier(&pbdev->shutdown_notifier);
-                qemu_register_reset(s390_pci_reset_cb, pbdev);
             }
         } else {
             pbdev->fh |= FH_SHM_EMUL;
@@ -1279,6 +1270,23 @@ static void s390_pci_enumerate_bridge(PCIBus *bus, 
PCIDevice *pdev,
     pci_default_write_config(pdev, PCI_SUBORDINATE_BUS, s->bus_no, 1);
 }
 
+void s390_pci_ism_reset(void)
+{
+    S390pciState *s = s390_get_phb();
+
+    S390PCIBusDevice *pbdev, *next;
+
+    /* Trigger reset event for each passthrough ISM device currently in-use */
+    QTAILQ_FOREACH_SAFE(pbdev, &s->zpci_devs, link, next) {
+        if (pbdev->interp && pbdev->pft == ZPCI_PFT_ISM &&
+            pbdev->fh & FH_MASK_ENABLE) {
+            s390_pci_kvm_aif_disable(pbdev);
+
+            pci_device_reset(pbdev->pdev);
+        }
+    }
+}
+
 static void s390_pcihost_reset(DeviceState *dev)
 {
     S390pciState *s = S390_PCI_HOST_BRIDGE(dev);
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index eaf61d3640..c99682b07d 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -118,6 +118,14 @@ static void subsystem_reset(void)
     DeviceState *dev;
     int i;
 
+    /*
+     * ISM firmware is sensitive to unexpected changes to the IOMMU, which can
+     * occur during reset of the vfio-pci device (unmap of entire aperture).
+     * Ensure any passthrough ISM devices are reset now, while CPUs are paused
+     * but before vfio-pci cleanup occurs.
+     */
+    s390_pci_ism_reset();
+
     for (i = 0; i < ARRAY_SIZE(reset_dev_types); i++) {
         dev = DEVICE(object_resolve_path_type("", reset_dev_types[i], NULL));
         if (dev) {
diff --git a/include/hw/s390x/s390-pci-bus.h b/include/hw/s390x/s390-pci-bus.h
index 435e788867..2c43ea123f 100644
--- a/include/hw/s390x/s390-pci-bus.h
+++ b/include/hw/s390x/s390-pci-bus.h
@@ -401,5 +401,6 @@ S390PCIBusDevice *s390_pci_find_dev_by_target(S390pciState 
*s,
                                               const char *target);
 S390PCIBusDevice *s390_pci_find_next_avail_dev(S390pciState *s,
                                                S390PCIBusDevice *pbdev);
+void s390_pci_ism_reset(void);
 
 #endif
-- 
2.43.0