> -----Original Message----- > From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] On > Behalf Of Joerg Roedel > Sent: Thursday, September 08, 2011 12:49 AM > To: Greg KH > Cc: Joerg Roedel; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; Alex Williamson; Ohad > Ben-Cohen; David Woodhouse; David Brown; kvm@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 02/10] Driver core: Add iommu_ops to bus_type > > Hi Greg, > > the bus_set_iommu() function will be called by the IOMMU driver. There > can be different drivers for the same bus, depending on the hardware. On > PCI for example, there can be the Intel or the AMD IOMMU driver that > implement the iommu-api and that register for that bus. > > On Wed, Sep 07, 2011 at 11:47:50AM -0700, Greg KH wrote: > > > +#ifdef CONFIG_IOMMU_API > > > +int bus_set_iommu(struct bus_type *bus, struct iommu_ops *ops) { > > > + if (bus->iommu_ops != NULL) > > > + return -EBUSY; > > > > Busy? > > Yes, it signals to the IOMMU driver that another driver has already > registered for that bus. In the previous register_iommu() interface this > was just a BUG(), but I think returning an error to the caller is better. > It can be turned back into a BUG() if it is considered better, though. > > > > + > > > + bus->iommu_ops = ops; > > > + > > > + /* Do IOMMU specific setup for this bus-type */ > > > + iommu_bus_init(bus, ops); > > > + > > > + return 0; > > > +} > > > +EXPORT_SYMBOL_GPL(bus_set_iommu); > > > > I don't understand what this function is for, and who would call it. > > It is called by the IOMMU driver. > > > Please provide kerneldoc that explains this. > > Will do. > > > > @@ -67,6 +68,9 @@ extern void bus_remove_file(struct bus_type *, > struct bus_attribute *); > > > * @resume: Called to bring a device on this bus out of sleep mode. > > > * @pm: Power management operations of this bus, callback > the specific > > > * device driver's pm-ops. > > > + * @iommu_ops IOMMU specific operations for this bus, used to > attach IOMMU > > > + * driver implementations to a bus and allow the driver > to do > > > + * bus-specific setup > > > > So why is this just not set by the bus itself, making the above > > function not needed at all? > > The IOMMUs are usually devices on the bus itself, so they are initialized > after the bus is set up and the devices on it are populated. So the > function can not be called on bus initialization because the IOMMU is not > ready at this point. Well, at what point would the add_device_group (referring to patch set posted by Alex) call back be invoked? -Varun -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
