[PATCH v2] piix: fix regression during unplug in Xen HVM domUs

[Olaf Hering <olaf@aepfle.de>]

Commit ee358e919e385fdc79d59d0d47b4a81e349cd5c9 causes a regression in
Xen HVM domUs which run xenlinux based kernels.

If the domU has an USB device assigned, for example with
"usbdevice=['tablet']" in domU.cfg, the late unplug of devices will
kill the emulated USB host. As a result the khubd thread hangs, and as
a result the entire boot process.

For some reason this does not affect pvops based kernels. This is
most likely caused by the fact that unplugging happens very early
during boot.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
 hw/ide/piix.c        | 5 +++++
 include/hw/ide/pci.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/hw/ide/piix.c b/hw/ide/piix.c
index b9860e35a5..7f1998bf04 100644
--- a/hw/ide/piix.c
+++ b/hw/ide/piix.c
@@ -109,6 +109,9 @@ static void piix_ide_reset(DeviceState *dev)
     uint8_t *pci_conf = pd->config;
     int i;
 
+    if (d->xen_unplug_done == true) {
+        return;
+    }
     for (i = 0; i < 2; i++) {
         ide_bus_reset(&d->bus[i]);
     }
@@ -151,6 +154,7 @@ static void pci_piix_ide_realize(PCIDevice *dev, Error **errp)
     PCIIDEState *d = PCI_IDE(dev);
     uint8_t *pci_conf = dev->config;
 
+    d->xen_unplug_done = false;
     pci_conf[PCI_CLASS_PROG] = 0x80; // legacy ATA mode
 
     bmdma_setup_bar(d);
@@ -170,6 +174,7 @@ int pci_piix3_xen_ide_unplug(DeviceState *dev, bool aux)
     BlockBackend *blk;
 
     pci_ide = PCI_IDE(dev);
+    pci_ide->xen_unplug_done = true;
 
     for (i = aux ? 1 : 0; i < 4; i++) {
         idebus = &pci_ide->bus[i / 2];
diff --git a/include/hw/ide/pci.h b/include/hw/ide/pci.h
index d8384e1c42..9e71cfec3b 100644
--- a/include/hw/ide/pci.h
+++ b/include/hw/ide/pci.h
@@ -50,6 +50,7 @@ struct PCIIDEState {
     IDEBus bus[2];
     BMDMAState bmdma[2];
     uint32_t secondary; /* used only for cmd646 */
+    bool xen_unplug_done;
     MemoryRegion bmdma_bar;
     MemoryRegion cmd_bar[2];
     MemoryRegion data_bar[2];