[PATCH v7 2/2] s390x/pci: Reset a device in error state

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

For passthrough devices in error state, for a guest driven reset of the
device we can attempt a reset to recover the device. A reset of the device
will trigger a CLP disable/enable cycle on the host to bring the device
into a recovered state.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
 hw/s390x/s390-pci-bus.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index b2967dacba..6557ec4240 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -1505,6 +1505,21 @@ static void s390_pci_device_reset(DeviceState *dev)
         return;
     case ZPCI_FS_STANDBY:
         break;
+    case ZPCI_FS_ERROR:
+        /*
+         * Attempt a reset to recover the device. A device in ERROR state
+         * can be transitioned to ENABLED or DISABLED state via guest
+         * driven actions.  Since this code path is also executed on
+         * subsystem_reset() and the expected state of a configured device
+         * after subsystem_reset() is to be in a DISABLED state, we need to
+         * transition from ERROR to DISABLED.
+         *
+         * Linux guests drive the state transition from ERROR to DISABLED
+         * via CLP_SET_DISABLE_PCI_FN. So it should be safe to transition
+         * from ERROR to DISABLED state.
+         */
+        pci_device_reset(pbdev->pdev);
+        /* fallthrough */
     default:
         pbdev->fh &= ~FH_MASK_ENABLE;
         pbdev->state = ZPCI_FS_DISABLED;
-- 
2.43.0