From 05af6159ba18882c0bdef512abd3c852b515430b Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Wed, 13 Jun 2018 14:07:30 +0200
Subject: [PATCH 03/57] usb-host: skip open on pending postload bh

RH-Author: Gerd Hoffmann <kraxel@redhat.com>
Message-id: <20180613140730.16401-2-kraxel@redhat.com>
Patchwork-id: 80667
O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 1/1] usb-host: skip open on pending postload bh
Bugzilla: 1572851
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

usb-host emulates a device unplug after live migration, because the
device state is unknown and unplug/replug makes sure the guest
re-initializes the device into a working state.  This can't be done in
post-load though, so post-load just schedules a bottom half which
executes after vmload is complete.

It can happen that the device autoscan timer hits the race window
between scheduling and running the bottom half, which in turn can
triggers an assert().

Fix that issue by just ignoring the usb_host_open() call in case the
bottom half didn't execute yet.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1572851
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20180503062932.17233-1-kraxel@redhat.com
(cherry picked from commit 3280ea8edede3814553aa19fa27a58daedd48ad9)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/usb/host-libusb.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/hw/usb/host-libusb.c b/hw/usb/host-libusb.c
index 1b0be07..0290fb8 100644
--- a/hw/usb/host-libusb.c
+++ b/hw/usb/host-libusb.c
@@ -102,6 +102,7 @@ struct USBHostDevice {
     /* callbacks & friends */
     QEMUBH                           *bh_nodev;
     QEMUBH                           *bh_postld;
+    bool                             bh_postld_pending;
     Notifier                         exit;
 
     /* request queues */
@@ -866,6 +867,10 @@ static int usb_host_open(USBHostDevice *s, libusb_device *dev)
     int rc;
     Error *local_err = NULL;
 
+    if (s->bh_postld_pending) {
+        return -1;
+    }
+
     trace_usb_host_open_started(bus_num, addr);
 
     if (s->dh != NULL) {
@@ -1524,6 +1529,7 @@ static void usb_host_post_load_bh(void *opaque)
     if (udev->attached) {
         usb_device_detach(udev);
     }
+    dev->bh_postld_pending = false;
     usb_host_auto_check(NULL);
 }
 
@@ -1535,6 +1541,7 @@ static int usb_host_post_load(void *opaque, int version_id)
         dev->bh_postld = qemu_bh_new(usb_host_post_load_bh, dev);
     }
     qemu_bh_schedule(dev->bh_postld);
+    dev->bh_postld_pending = true;
     return 0;
 }
 
-- 
1.8.3.1