On Wed, Dec 10, 2014 at 08:43:55PM +0100, Igor Mammedov wrote: > On Wed, 10 Dec 2014 20:28:01 +0200 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > On Wed, Dec 10, 2014 at 06:39:49PM +0100, Igor Mammedov wrote: > > > On Wed, 10 Dec 2014 19:13:59 +0200 > > > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > > > > > On Wed, Dec 10, 2014 at 05:45:58PM +0100, Igor Mammedov wrote: > > > > > On Wed, 10 Dec 2014 18:24:24 +0200 > > > > > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > > > > > > > > > On Wed, Dec 10, 2014 at 04:06:56PM +0000, Igor Mammedov wrote: > > > > > > > linker and RSDP tables are build only once, so if later > > > > > > > during rebuild sizes of other ACPI tables change > > > > > > > pointers will be patched incorrectly due to wrong > > > > > > > offsets. > > > > > > > > > > > > > > To fix it rebuild linker and RSDP tables along with > > > > > > > the rest of ACPI tables so that they would have correct > > > > > > > offsets. > > > > > > > > > > > > > > Here is a simple reproducer: > > > > > > > 1: hotplug bridge using command: > > > > > > > device_add pci-bridge,chassis_nr=1 > > > > > > > 2: reset system from monitor: > > > > > > > system_reset > > > > > > > > > > > > > > As result pointers to ACPI tables are not correct > > > > > > > and guest can't read/parse ACPI tables. > > > > > > > Windows guests just refuse to boot and > > > > > > > Linux guests are more resilient and try to boot without > > > > > > > ACPI, sometimes successfully. > > > > > > > > > > > > > > PS: > > > > > > > keep brokenness in 2.2 and older machine types for the sake > > > > > > > of migration > > > > > > > > > > > > > > Signed-off-by: Igor Mammedov <imamm...@redhat.com> > > > > > > > > > > > > I'd like to fix 2.2 as well. > > > > > that's easy, > > > > > has_imutable_rsdp = true > > > > > should be moved into > > > > > pc_compat_2_1() > > > > > > > > > > > > > > > > > Why does adding bridge in this way cause tables to > > > > > > be resized? > > > > > > I think this is a root-cause that should be fixed. > > > > > That's because there wasn't any bridge described in tables > > > > > on startup, but after hotplug and reset tables are rebuild > > > > > which pickups hotplugged bridge and its secondary PCI bus. > > > > > > > > > > This behavior seems sane, I'd expect bare-metal behave > > > > > the same way. > > > > > > > > For a simple fix, we can skip bridges added by hotplug - > > > > treat them as regular devices. > > > > > > > > It defintely seems nicer - at least for old machine types - > > > > than "keep brokenness". > > > > > > > > I think the following should do the trcik, but it's completely > > > > untested. > > > > Could you pls try? > > > > > > > > > > > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c > > > > index b37a397..039776d 100644 > > > > --- a/hw/i386/acpi-build.c > > > > +++ b/hw/i386/acpi-build.c > > > > @@ -844,7 +844,8 @@ static void build_pci_bus_end(PCIBus *bus, > > > > void *bus_state) > > > > * Skip bridge subtree creation if bridge hotplug is disabled > > > > * to make acpi tables compatible with legacy machine types. > > > > */ > > > > - if (!child->pcihp_bridge_en && bus->parent_dev) { > > > > + if (bus->parent_dev && (!child->pcihp_bridge_en || > > > > + !DEVICE(bus->parent_dev)->hotplugged)) > > > > { return; > > > > } > > > What will happen if > > > hotplug may bridges in > > > QEMU-fixed^^ -M 2.1 > > > migrate to target: > > > QEMU-2.1 -M 2.1 + hotplugged on sourcebridges on CLI > > > > > > My guess it may fail due to ACPI blob size difference. > > > > Yes it might if we are unlucky and cross a 64 k boundary. > > The robust fix is still to resize ROMs on receive. > > We'll also put this patch on a stable branch. > > > > Well, in my opinion though above snippet is sipmlier but it's papering > over the bug in table linker and RSDP, instead of fixing it.
I'm not against making the change for new machine types, but I'm also looking for a fix for 2.2.1 > In this case SSDT size change is quite legetimate and in future there > could be other cases when it changes. So it would be better fix the root > problem which is corrupting tables due to changed SSDT size on reboot > instead of pretending that issue doesn't exist. For -M 2.3 and up, I'm fine with this approach generally. Of course it all only works on the assumption we make ROM regions resizeable. If not your patch creates migration problems: -hot-add bridge on source -hot-add on destination Size now depends on whether source rebooted, destination has no way to know that. -- MST