[Qemu-devel] Re: [PATCH v2 0/6] qdev reset refactoring and pci bus reset

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Nov 23, 2010 at 12:53:12AM +0200, Michael S. Tsirkin wrote:
> On Mon, Nov 22, 2010 at 07:43:37PM +0900, Isaku Yamahata wrote:
> > On Mon, Nov 22, 2010 at 09:54:02AM +0200, Michael S. Tsirkin wrote:
> > > On Fri, Nov 19, 2010 at 06:55:57PM +0900, Isaku Yamahata wrote:
> > > > Here is v2. I updated the comments, and dropped the pci qdev reset patch.
> > > > 
> > > > Patch description:
> > > > The goal of this patch series is to implement secondary bus reset
> > > > emulation in pci-to-pci bridge.
> > > > At first, this patch series refactors qdev reset,
> > > > and then cleans up pci bus reset. Lastly implements pci bridge control
> > > > secondary bus reset bit.
> > > > 
> > > > This patch series is for pci bus reset, which is ported
> > > > from the following repo.
> > > > git://repo.or.cz/qemu/aliguori.git qdev-refactor
> > > 
> > > I've put the series on my pci branch, tweaking patches 5 and 6 in the
> > > process.  Out of time to compile-tested only for now.
> > 
> > Thank you. The tweaking looks good.
> > Do you still want me to send another patch to add a comment on RST#?
> 
> OK, I got response, and yes, we need to fix code to avoid claiming
> transactions by devices on the secondary bus while secondary bus is in
> RST# for both pci and express.

I guess the following fixes it?

--->

pci: don't access bus while it's reset

Devices on a bus should not respond while RST#
is asserted, which is controlled by PCI_BRIDGE_CTL_BUS_RESET.
Simply skip such a bus when propagating the configuration cycle.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

diff --git a/hw/pci.c b/hw/pci.c
index d02f980..60bdded 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1554,7 +1554,9 @@ PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
 
     /* try child bus */
     if (!bus->parent_dev /* host pci bridge */ ||
-        (bus->parent_dev->config[PCI_SECONDARY_BUS] < bus_num &&
+        (!(pci_get_word(bus->parent_dev->config + PCI_BRIDGE_CONTROL) &
+           PCI_BRIDGE_CTL_BUS_RESET) /* Don't walk the bus if it's reset. */ &&
+         bus->parent_dev->config[PCI_SECONDARY_BUS] < bus_num &&
          bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS])) {
         for (; bus; bus = sec) {
             QLIST_FOREACH(sec, &bus->child, sibling) {