[Xen-changelog] [xen-unstable] vtd: Don't do FLR when we create domain or hotplug device into guest.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1219139501 -3600
# Node ID 7c10be016e432163c8d95a9d5a79636ff6133e93
# Parent  2af894d8cecd04ae8bdf298172c5196df42e2f3f
vtd: Don't do FLR when we create domain or hotplug device into guest.

VT-d hot-plug is done in such a way:  1) xend sends 'pci-ins' command
to ioemu via xenstore; 2) ioemu creates pass-through device and raises
SCI to guest OS; guest OS loads device driver, and device driver
initializes the hot-plugged device; 3) xend does FLR. There is a race
condition about 2) and 3). If 3) runs slow, we have troubles. Thanks
for Yuji Shimada's locating the issues.

We can work around the issues by not doing FLR when we create domain
or hotplug device into guest, namely, we only do FLR when we destroy
domain or hotplug device from guest.

Signed-off-by: Dexuan Cui <dexuan.cui@xxxxxxxxx>
Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
---
 tools/python/xen/xend/server/pciif.py |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff -r 2af894d8cecd -r 7c10be016e43 tools/python/xen/xend/server/pciif.py
--- a/tools/python/xen/xend/server/pciif.py     Tue Aug 19 10:48:39 2008 +0100
+++ b/tools/python/xen/xend/server/pciif.py     Tue Aug 19 10:51:41 2008 +0100
@@ -290,8 +290,12 @@ class PciController(DevController):
 
         self.CheckSiblingDevices(fe_domid, dev)
 
-        if arch.type != "ia64":
-            dev.do_FLR()
+        # We don't do FLR when we create domain and hotplug device into guest,
+        # namely, we only do FLR when we destroy domain or hotplug device from
+        # guest. This is mainly to work around the race condition in hotplug 
code
+        # paths. See the changeset's description for details.
+        # if arch.type != "ia64":
+        #    dev.do_FLR()
 
         PCIQuirk(dev.vendor, dev.device, dev.subvendor, dev.subdevice, domain, 
                 bus, slot, func)

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