[PATCH] s390x/pci: reset ISM passthrough devices on shutdown and system reset

[Matthew Rosato]

ISM device firmware stores unique state information that can
can cause a wholesale unmap of the associated IOMMU (e.g. when
we get a termination signal for QEMU) to trigger firmware errors
because firmware believes we are attempting to invalidate entries
that are still in-use by the guest OS (when in fact that guest is
in the process of being terminated or rebooted).
To alleviate this, register both a shutdown notifier (for unexpected
termination cases e.g. virsh destroy) as well as a reset callback
(for cases like guest OS reboot).  For each of these scenarios, trigger
PCI device reset; this is enough to indicate to firmware that the IOMMU
is no longer in-use by the guest OS, making it safe to invalidate any
associated IOMMU entries.

Fixes: 15d0e7942d3b ("s390x/pci: don't fence interpreted devices without MSI-X")
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 hw/s390x/s390-pci-bus.c         | 28 ++++++++++++++++++++++++++++
 hw/s390x/s390-pci-vfio.c        |  2 ++
 include/hw/s390x/s390-pci-bus.h |  5 +++++
 3 files changed, 35 insertions(+)

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index 977e7daa15..02751f3597 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -24,6 +24,8 @@
 #include "hw/pci/msi.h"
 #include "qemu/error-report.h"
 #include "qemu/module.h"
+#include "sysemu/reset.h"
+#include "sysemu/runstate.h"
 
 #ifndef DEBUG_S390PCI_BUS
 #define DEBUG_S390PCI_BUS  0
@@ -150,10 +152,30 @@ out:
     psccb->header.response_code = cpu_to_be16(rc);
 }
 
+static void s390_pci_shutdown_notifier(Notifier *n, void *opaque)
+{
+    S390PCIBusDevice *pbdev = container_of(n, S390PCIBusDevice,
+                                           shutdown_notifier);
+
+    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 */
     if (pbdev->pdev) {
         DeviceState *pdev = DEVICE(pbdev->pdev);
@@ -1111,6 +1133,12 @@ static void s390_pcihost_plug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
                 pbdev->fh |= FH_SHM_VFIO;
                 pbdev->forwarding_assist = false;
             }
+            /* Register shutdown notifier and reset callback for ISM devices */
+            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;
             /* Always intercept emulated devices */
diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
index 5f0adb0b4a..419763f829 100644
--- a/hw/s390x/s390-pci-vfio.c
+++ b/hw/s390x/s390-pci-vfio.c
@@ -122,6 +122,8 @@ static void s390_pci_read_base(S390PCIBusDevice *pbdev,
     /* The following values remain 0 until we support other FMB formats */
     pbdev->zpci_fn.fmbl = 0;
     pbdev->zpci_fn.pft = 0;
+    /* Store function type separately for type-specific behavior */
+    pbdev->pft = cap->pft;
 }
 
 static bool get_host_fh(S390PCIBusDevice *pbdev, struct vfio_device_info *info,
diff --git a/include/hw/s390x/s390-pci-bus.h b/include/hw/s390x/s390-pci-bus.h
index 0605fcea24..4c812c65db 100644
--- a/include/hw/s390x/s390-pci-bus.h
+++ b/include/hw/s390x/s390-pci-bus.h
@@ -39,6 +39,9 @@
 #define UID_CHECKING_ENABLED 0x01
 #define ZPCI_DTSM 0x40
 
+/* zPCI Function Types */
+#define ZPCI_PFT_ISM 5
+
 OBJECT_DECLARE_SIMPLE_TYPE(S390pciState, S390_PCI_HOST_BRIDGE)
 OBJECT_DECLARE_SIMPLE_TYPE(S390PCIBus, S390_PCI_BUS)
 OBJECT_DECLARE_SIMPLE_TYPE(S390PCIBusDevice, S390_PCI_DEVICE)
@@ -343,6 +346,7 @@ struct S390PCIBusDevice {
     uint16_t noi;
     uint16_t maxstbl;
     uint8_t sum;
+    uint8_t pft;
     S390PCIGroup *pci_group;
     ClpRspQueryPci zpci_fn;
     S390MsixInfo msix;
@@ -351,6 +355,7 @@ struct S390PCIBusDevice {
     MemoryRegion msix_notify_mr;
     IndAddr *summary_ind;
     IndAddr *indicator;
+    Notifier shutdown_notifier;
     bool pci_unplug_request_processed;
     bool unplug_requested;
     bool interp;
-- 
2.38.1