pcie: fast unplug when slot power is off

In case the slot is powered off (and the power indicator turned off too)
we can unplug right away, without round-trip to the guest.

Also clear pending attention button press, there is nothing to care
about any more.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20211111130859.1171890-6-kraxel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci/pcie.c

@@ -560,6 +560,16 @@ void pcie_cap_slot_unplug_request_cb(HotplugHandler *hotplug_dev,
         return;
     }
 
+    if (((sltctl & PCI_EXP_SLTCTL_PIC) == PCI_EXP_SLTCTL_PWR_IND_OFF) &&
+        ((sltctl & PCI_EXP_SLTCTL_PCC) == PCI_EXP_SLTCTL_PWR_OFF)) {
+        /* slot is powered off -> unplug without round-trip to the guest */
+        pcie_cap_slot_do_unplug(hotplug_pdev);
+        hotplug_event_notify(hotplug_pdev);
+        pci_word_test_and_clear_mask(exp_cap + PCI_EXP_SLTSTA,
+                                     PCI_EXP_SLTSTA_ABP);
+        return;
+    }
+
     pcie_cap_slot_push_attention_button(hotplug_pdev);
 }