On Sat, Nov 05, 2016 at 06:46:34PM +0200, Marcel Apfelbaum wrote: > On 11/03/2016 09:40 PM, Michael S. Tsirkin wrote: > > On Thu, Nov 03, 2016 at 01:05:44PM +0200, Marcel Apfelbaum wrote: > > > On 11/03/2016 06:18 AM, Michael S. Tsirkin wrote: > > > > On Wed, Nov 02, 2016 at 05:16:42PM +0200, Marcel Apfelbaum wrote: > > > > > The shpc component is optional while ACPI hotplug is used > > > > > for hot-plugging PCI devices into a PCI-PCI bridge. > > > > > Disabling the shpc by default will make slot 0 usable at boot time > > > > > > Hi Michael > > > > > > > > > > > at the cost of breaking all hotplug for all non-acpi users. > > > > > > > > > > Do we have a non-acpi user that is able to use the shpc component as-is > > > today? > > > > power and some arm systems I guess? > > > > Adding Andrew , maybe he can give us an answer.
Not really :-) My lack of PCI knowledge makes that difficult. I'd be happy to help with an experiment though. Can you give me command line arguments, qmp commands, etc. that I should use to try it out? I imagine I should just boot an ARM guest using DT (instead of ACPI) and then attempt to hotplug a PCI device. I'm not sure, however, what, if any, special configuration I need in order to ensure I'm testing what you're interested in. Thanks, drew > > Anybody else can help answering this? > > > > I remember we need to even tweak QEMU before it can be used, but I might > > > be wrong. > > > > > > And we don't touch the current machines < 2.8 . > > > > > > > > and not only for hot-plug, without loosing any functionality. > > > > > Older machines will have shpc enabled for compatibility reasons. > > > > > > > > > > Signed-off-by: Marcel Apfelbaum <mar...@redhat.com> > > > > > > > > Is an extra slot such a big deal? You can always add more bridges ... > > > > > > > > > > It is not only about the slot itself, but more about the usage model. > > > The PCIe Upstream ports/DMI-PCI devices are also pci-bridges, > > > but for them slot 0 is allowed. > > > > The reason is that these devices are not themselves > > hotpluggable. Isn't there a flag that allows adding > > a non hotpluggable device? Allowing these would be one solution. > > > > > And what about the hotplug? Slot 0 is not usable at boot, but then is > > > usable again (for ACPI users) making people wondering: > > > https://bugzilla.redhat.com/show_bug.cgi?id=1175113 > > > > Let's just disallow that then for consistency? > > > > I suppose we can do that... not sure if it worth it. > > Thanks, > Marcel > > > > > > My point is - can shpc be used as-is today? Even so, I suspect there are > > > much (much) > > > less users using SHPC than ACPI based hotplug. If this is the case, why > > > bother the > > > majority of the users? And for the shpc users, they can keep the prev > > > machines > > > or change the command line, I think changes like this happens over the > > > time. > > > > > > Adding Markus for his opinion on command line changes. > > > > > > Thanks, > > > Marcel > > > > > --- > > > > > hw/pci-bridge/pci_bridge_dev.c | 2 +- > > > > > include/hw/compat.h | 4 ++++ > > > > > 2 files changed, 5 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/hw/pci-bridge/pci_bridge_dev.c > > > > > b/hw/pci-bridge/pci_bridge_dev.c > > > > > index 5dbd933..647ad80 100644 > > > > > --- a/hw/pci-bridge/pci_bridge_dev.c > > > > > +++ b/hw/pci-bridge/pci_bridge_dev.c > > > > > @@ -163,7 +163,7 @@ static Property pci_bridge_dev_properties[] = { > > > > > DEFINE_PROP_ON_OFF_AUTO(PCI_BRIDGE_DEV_PROP_MSI, PCIBridgeDev, > > > > > msi, > > > > > ON_OFF_AUTO_AUTO), > > > > > DEFINE_PROP_BIT(PCI_BRIDGE_DEV_PROP_SHPC, PCIBridgeDev, flags, > > > > > - PCI_BRIDGE_DEV_F_SHPC_REQ, true), > > > > > + PCI_BRIDGE_DEV_F_SHPC_REQ, false), > > > > > DEFINE_PROP_END_OF_LIST(), > > > > > }; > > > > > > > > > > diff --git a/include/hw/compat.h b/include/hw/compat.h > > > > > index 0f06e11..388b7ec 100644 > > > > > --- a/include/hw/compat.h > > > > > +++ b/include/hw/compat.h > > > > > @@ -18,6 +18,10 @@ > > > > > .driver = "intel-iommu",\ > > > > > .property = "x-buggy-eim",\ > > > > > .value = "true",\ > > > > > + },{\ > > > > > + .driver = "pci-bridge",\ > > > > > + .property = "shpc",\ > > > > > + .value = "on",\ > > > > > }, > > > > > > > > > > #define HW_COMPAT_2_6 \ > > > > > -- > > > > > 2.5.5 > >
