[PATCH] hw/pci/pcie: Move hot plug capability check to pre_plug callback

[Julia Suvorova <jusual@redhat.com>]

Check for hot plug capability earlier to avoid removing devices attached
during the initialization process.

Run qemu with an unattached drive:
  -drive file=$FILE,if=none,id=drive0 \
  -device pcie-root-port,id=rp0,slot=3,bus=pcie.0,hotplug=off
Hotplug a block device:
  device_add virtio-blk-pci,id=blk0,drive=drive0,bus=rp0
If hotplug fails on plug_cb, drive0 will be deleted.

Signed-off-by: Julia Suvorova <jusual@redhat.com>
---
Hard to say if it's a bug or generally acceptable behaviour, but seems like
hotplug_handler_plug should never fail.

 hw/pci/pcie.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index f50e10b8fb..5b9c022d91 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -407,6 +407,17 @@ static void pcie_cap_slot_plug_common(PCIDevice *hotplug_dev, DeviceState *dev,
 void pcie_cap_slot_pre_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
                                Error **errp)
 {
+    PCIDevice *hotplug_pdev = PCI_DEVICE(hotplug_dev);
+    uint8_t *exp_cap = hotplug_pdev->config + hotplug_pdev->exp.exp_cap;
+    uint32_t sltcap = pci_get_word(exp_cap + PCI_EXP_SLTCAP);
+
+    /* Check if hot-plug is disabled on the slot */
+    if (dev->hotplugged && (sltcap & PCI_EXP_SLTCAP_HPC) == 0) {
+        error_setg(errp, "Hot-plug failed: unsupported by the port device '%s'",
+                         DEVICE(hotplug_pdev)->id);
+        return;
+    }
+
     pcie_cap_slot_plug_common(PCI_DEVICE(hotplug_dev), dev, errp);
 }
 
@@ -415,7 +426,6 @@ void pcie_cap_slot_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
 {
     PCIDevice *hotplug_pdev = PCI_DEVICE(hotplug_dev);
     uint8_t *exp_cap = hotplug_pdev->config + hotplug_pdev->exp.exp_cap;
-    uint32_t sltcap = pci_get_word(exp_cap + PCI_EXP_SLTCAP);
     PCIDevice *pci_dev = PCI_DEVICE(dev);
 
     /* Don't send event when device is enabled during qemu machine creation:
@@ -431,13 +441,6 @@ void pcie_cap_slot_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
         return;
     }
 
-    /* Check if hot-plug is disabled on the slot */
-    if ((sltcap & PCI_EXP_SLTCAP_HPC) == 0) {
-        error_setg(errp, "Hot-plug failed: unsupported by the port device '%s'",
-                         DEVICE(hotplug_pdev)->id);
-        return;
-    }
-
     /* To enable multifunction hot-plug, we just ensure the function
      * 0 added last. When function 0 is added, we set the sltsta and
      * inform OS via event notification.
-- 
2.25.4