pcie: add power indicator blink check

Refuse to push the attention button in case the guest is busy with some
hotplug operation (as indicated by the power indicator blinking).

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20211111130859.1171890-4-kraxel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci/pcie.c

@@ -506,6 +506,7 @@ void pcie_cap_slot_unplug_request_cb(HotplugHandler *hotplug_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);
+    uint16_t sltctl = pci_get_word(exp_cap + PCI_EXP_SLTCTL);
 
     /* Check if hot-unplug is disabled on the slot */
     if ((sltcap & PCI_EXP_SLTCAP_HPC) == 0) {
@@ -521,6 +522,12 @@ void pcie_cap_slot_unplug_request_cb(HotplugHandler *hotplug_dev,
         return;
     }
 
+    if ((sltctl & PCI_EXP_SLTCTL_PIC) == PCI_EXP_SLTCTL_PWR_IND_BLINK) {
+        error_setg(errp, "Hot-unplug failed: "
+                   "guest is busy (power indicator blinking)");
+        return;
+    }
+
     dev->pending_deleted_event = true;
 
     /* In case user cancel the operation of multi-function hot-add,