[Qemu-devel] [PATCH v2 2/3] VFIO: Disable INTx interrupt on EEH reset

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

When Linux guest recovers from EEH error on the following Emulex
adapter, the MSIx interrupts are disabled and the INTx emulation
is enabled. One INTx interrupt is injected to the guest by host
because of detected pending INTx interrupts on the adapter. QEMU
disables mmap'ed BAR regions and starts a timer to enable those
regions at later point the INTx interrupt handler. Unfortunately,
"VFIOPCIDevice->intx.pending" isn't cleared, meaning those disabled
mapp'ed BAR regions won't be reenabled properly. It leads to EEH
recovery failure at guest side because of hanged MMIO access.

 # lspci | grep Emulex
 0000:01:00.0 Ethernet controller: Emulex Corporation \
              OneConnect 10Gb NIC (be3) (rev 02)
 0000:01:00.1 Ethernet controller: Emulex Corporation \
              OneConnect 10Gb NIC (be3) (rev 02)

The patch disables INTx interrupt before doing EEH reset to avoid
the issue.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
---
 hw/vfio/pci.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index fca1edc..bfa3d0c 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3340,6 +3340,14 @@ int vfio_container_eeh_event(AddressSpace *as, int32_t groupid,
          * disable it so that it can be reenabled properly. Also,
          * the cached MSIx table should be cleared as it's not
          * reflecting the contents in hardware.
+         *
+         * We might have INTx interrupt whose handler disables the
+         * memory mapped BARs. The INTx pending state can't be
+         * cleared with memory BAR access in slow path. The timer
+         * kicked by the INTx interrupt handler won't enable those
+         * disabled memory mapped BARs, which leads to hanged MMIO
+         * register access and EEH recovery failure. We simply disable
+         * INTx if it has been enabled.
          */
         QLIST_FOREACH(vbasedev, &group->device_list, next) {
             vdev = container_of(vbasedev, VFIOPCIDevice, vbasedev);
@@ -3348,6 +3356,11 @@ int vfio_container_eeh_event(AddressSpace *as, int32_t groupid,
             }
 
             msix_reset(&vdev->pdev);
+
+            /* Disable INTx */
+            if (vdev->interrupt == VFIO_INT_INTx) {
+                vfio_disable_intx(vdev);
+            }
         }
 
         break;
-- 
1.8.3.2