[PATCH v1] 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 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/ide/piix.c b/hw/ide/piix.c
index b9860e35a5..2a380a90e9 100644
--- a/hw/ide/piix.c
+++ b/hw/ide/piix.c
@@ -34,6 +34,7 @@
 #include "hw/ide/pci.h"
 #include "trace.h"
 
+static bool pci_piix3_xen_ide_unplug_done;
 static uint64_t bmdma_read(void *opaque, hwaddr addr, unsigned size)
 {
     BMDMAState *bm = opaque;
@@ -109,6 +110,8 @@ static void piix_ide_reset(DeviceState *dev)
     uint8_t *pci_conf = pd->config;
     int i;
 
+    if (pci_piix3_xen_ide_unplug_done == true)
+        return;
     for (i = 0; i < 2; i++) {
         ide_bus_reset(&d->bus[i]);
     }
@@ -169,6 +172,7 @@ int pci_piix3_xen_ide_unplug(DeviceState *dev, bool aux)
     IDEBus *idebus;
     BlockBackend *blk;
 
+    pci_piix3_xen_ide_unplug_done = true;
     pci_ide = PCI_IDE(dev);
 
     for (i = aux ? 1 : 0; i < 4; i++) {
@@ -259,6 +263,7 @@ static const TypeInfo piix4_ide_info = {
 
 static void piix_ide_register_types(void)
 {
+    pci_piix3_xen_ide_unplug_done = false;
     type_register_static(&piix3_ide_info);
     type_register_static(&piix3_ide_xen_info);
     type_register_static(&piix4_ide_info);