On Monday, September 09, 2013 10:32:57 AM Alex Williamson wrote: > On Sun, 2013-09-08 at 00:16 +0200, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > > > In the current ACPIPHP notify handler we always go directly for a > > rescan of the parent bus if we get a device check notification for > > a device that is not a bridge. However, this obviously is > > overzealous if nothing really changes, because this way we may rescan > > the whole PCI hierarchy pretty much in vain. > > > > That happens on Alex Williamson's machine whose ACPI tables contain > > device objects that are supposed to coresspond to PCIe root ports, > > but those ports aren't physically present (or at least they aren't > > visible in the PCI config space to us). The BIOS generates multiple > > device check notifies for those objects during boot and for each of > > them we go straight for the parent bus rescan, but the parent bus is > > the root bus in this particular case. In consequence, we rescan the > > whole PCI bus from the top several times in a row, which is > > completely unnecessary, increases boot time by 50% (after previous > > fixes) and generates excess dmesg output from the PCI subsystem. > > > > Fix the problem by checking if we can find anything new in the > > slot corresponding to the device we've got a device check notify > > for and doing nothig if that's not the case. > > > > The spec (ACPI 5.0, Section 5.6.6) appears to mandate this behavior, > > as it says: > > > > Device Check. Used to notify OSPM that the device either appeared > > or disappeared. If the device has appeared, OSPM will re-enumerate > > from the parent. If the device has disappeared, OSPM will > > invalidate the state of the device. OSPM may optimize out > > re-enumeration. > > > > Therefore, according to the spec, we are free to do nothing if > > nothing changes. > > > > References: https://bugzilla.kernel.org/show_bug.cgi?id=60865 > > Reported-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > --- > > Works for me. Thanks! > > Tested-by: Alex Williamson <alex.williamson@xxxxxxxxxx> Great, thanks for testing. > > --- > > drivers/pci/hotplug/acpiphp_glue.c | 32 +++++++++++++++++++++++++------- > > 1 file changed, 25 insertions(+), 7 deletions(-) > > > > Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c > > =================================================================== > > --- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c > > +++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c > > @@ -528,6 +528,16 @@ static void check_hotplug_bridge(struct > > } > > } > > > > +static int acpiphp_rescan_slot(struct acpiphp_slot *slot) > > +{ > > + struct acpiphp_func *func; > > + > > + list_for_each_entry(func, &slot->funcs, sibling) > > + acpiphp_bus_add(func_to_handle(func)); > > + > > + return pci_scan_slot(slot->bus, PCI_DEVFN(slot->device, 0)); > > +} > > + > > /** > > * enable_slot - enable, configure a slot > > * @slot: slot to be enabled > > @@ -544,10 +554,7 @@ static void __ref enable_slot(struct acp > > LIST_HEAD(add_list); > > int nr_found; > > > > - list_for_each_entry(func, &slot->funcs, sibling) > > - acpiphp_bus_add(func_to_handle(func)); > > - > > - nr_found = pci_scan_slot(bus, PCI_DEVFN(slot->device, 0)); > > + nr_found = acpiphp_rescan_slot(slot); > > max = acpiphp_max_busnr(bus); > > for (pass = 0; pass < 2; pass++) { > > list_for_each_entry(dev, &bus->devices, bus_list) { > > @@ -840,11 +847,22 @@ static void hotplug_event(acpi_handle ha > > case ACPI_NOTIFY_DEVICE_CHECK: > > /* device check */ > > dbg("%s: Device check notify on %s\n", __func__, objname); > > - if (bridge) > > + if (bridge) { > > acpiphp_check_bridge(bridge); > > - else > > - acpiphp_check_bridge(func->parent); > > + } else { > > + struct acpiphp_slot *slot = func->slot; > > + int ret; > > > > + /* > > + * Check if anything has changed in the slot and rescan > > + * from the parent if that's the case. > > + */ > > + mutex_lock(&slot->crit_sect); > > + ret = acpiphp_rescan_slot(slot); > > + mutex_unlock(&slot->crit_sect); > > + if (ret) > > + acpiphp_check_bridge(func->parent); > > + } > > break; > > > > case ACPI_NOTIFY_EJECT_REQUEST: > > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
