[PULL 2/4] hw/nvme: fix assertion failure on subregion removal

[Klaus Jensen <its@irrelevant.dk>]

From: Daniel Paziyski <danielpaziyski@gmail.com>

When a controller is created with a MSI-X exclusive BAR, the bar0 memory region
is not used at all, and so, the iomem region is not added as a subregion of it.
However, when removing a NVMe controller, the iomem region is unconditionally
removed as a subregion of bar0, causing an assertion failure. Remove the iomem
memory region as a subregion of bar0 only if not using a MSI-X exclusive BAR.

QEMU options (requires a hotunplug-aware OS):

        -M q35 -device pcie-root-port,id=rp0 \
        -device nvme,serial=ctrl0,id=ctrl0,bus=rp0,msix-exclusive-bar=on

In the QEMU monitor, or by causing an ejection from the OS:

        device_del ctrl0

Message in stderr:

qemu-system-x86_64: ../system/memory.c:2617: memory_region_del_subregion: Assertion `subregion->container == mr' failed.

Fixes: fa905f65c554 ("hw/nvme: add machine compatibility parameter to enable msix exclusive bar")
Fixes: 9162f1012576 ("hw/nvme: fix msix_uninit with exclusive bar")
Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4090
Signed-off-by: Daniel Paziyski <danielpaziyski@gmail.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
---
 hw/nvme/ctrl.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 086048b689d3..e1639b3839f7 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -9703,10 +9703,9 @@ static void nvme_exit(PCIDevice *pci_dev)
         msix_uninit_exclusive_bar(pci_dev);
     } else {
         msix_uninit(pci_dev, &n->bar0, &n->bar0);
+        memory_region_del_subregion(&n->bar0, &n->iomem);
     }
 
-    memory_region_del_subregion(&n->bar0, &n->iomem);
-
     migrate_del_blocker(&n->migration_blocker);
 }
 
-- 
2.53.0