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[PATCH] failover: fix unplug pending detection

From: Laurent Vivier
Subject: [PATCH] failover: fix unplug pending detection
Date: Thu, 30 Sep 2021 10:20:32 +0200

Failover needs to detect the end of the PCI unplug to start migration
after the VFIO card has been unplugged.

To do that, a flag is set in pcie_cap_slot_unplug_request_cb() and reset in

But since
    17858a169508 ("hw/acpi/ich9: Set ACPI PCI hot-plug as default on Q35")
we have switched to ACPI unplug and these functions are not called anymore
and the flag not set. So failover migration is not able to detect if card
is really unplugged and acts as it's done as soon as it's started. So it
doesn't wait the end of the unplug to start the migration. We don't see any
problem when we test that because ACPI unplug is faster than PCIe native
hotplug and when the migration really starts the unplug operation is
already done.

See c000a9bd06ea ("pci: mark device having guest unplug request pending")
    a99c4da9fc2a ("pci: mark devices partially unplugged")

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
 hw/acpi/pcihp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
index f610a25d2ef9..a2d27a3c4763 100644
--- a/hw/acpi/pcihp.c
+++ b/hw/acpi/pcihp.c
@@ -366,6 +366,11 @@ void acpi_pcihp_device_unplug_cb(HotplugHandler 
*hotplug_dev, AcpiPciHpState *s,
+    if (pdev->partially_hotplugged) {
+        pdev->qdev.pending_deleted_event = false;
+        return;
+    }
      * clean up acpi-index so it could reused by another device
@@ -396,6 +401,7 @@ void acpi_pcihp_device_unplug_request_cb(HotplugHandler 
+    pdev->qdev.pending_deleted_event = true;
     s->acpi_pcihp_pci_status[bsel].down |= (1U << slot);
     acpi_send_event(DEVICE(hotplug_dev), ACPI_PCI_HOTPLUG_STATUS);

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