MSI: Robust resource release

msi_init may fail, so we need to check on uninit if the cap was
actually installed. This also avoids that the users need to check.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/hw/msi.c b/hw/msi.c
index 3dc3a24..b0795bd 100644
--- a/hw/msi.c
+++ b/hw/msi.c
@@ -164,9 +164,17 @@ int msi_init(struct PCIDevice *dev, uint8_t offset,
 
 void msi_uninit(struct PCIDevice *dev)
 {
-    uint16_t flags = pci_get_word(dev->config + msi_flags_off(dev));
-    uint8_t cap_size = msi_cap_sizeof(flags);
+    uint16_t flags;
+    uint8_t cap_size;
+
+    if (!(dev->cap_present & QEMU_PCI_CAP_MSI)) {
+        return;
+    }
+    flags = pci_get_word(dev->config + msi_flags_off(dev));
+    cap_size = msi_cap_sizeof(flags);
     pci_del_capability(dev, PCI_CAP_ID_MSIX, cap_size);
+    dev->cap_present &= ~QEMU_PCI_CAP_MSI;
+
     MSI_DEV_PRINTF(dev, "uninit\n");
 }