On Fri, 2012-10-26 at 12:15 +0200, Paolo Bonzini wrote: > > Whether you want to do startup configuration and board wiring via > > the same ioctl that handles runtime state save/load/migration is > > a different question, of course. > > QEMU's MSI-X routing is not x86-specific, so it should use the same > KVM_SET_GSI_ROUTING ioctl that x86 uses. Well, that's the thing, I haven't managed to figure that out so far, it looks very x86-specific to me. To begin with there's no such thing as a "GSI" in our world. Basically we have a global interrupt number space. Interrupt numbers are 24-bit long quantities. On real HW, some bits are called the "BUID" and identify a given source controller and some bits are the interrupt within that source controller but that's fairly flexible and generally the OS doesn't care about it. The firmware sets up the mappings and tells us the final numbers via the device-tree. Under a hypervisor, it's totally virtualized already so we show a flat 24 bit number space to the guest. MSIs don't work exactly like x86 either. On real HW, we have a different MSI port per "partitionable endpoint" which are use purely for validation of access permission. The message itself contain the interrupt source number within the BUID of the bridge. A given bridge today can contains up to 256 of these on a P7IOC chip but upcoming stuff can have thousands. The final interrupt number seen by the OS is thus just that MSI message in the bottom bits and the BUID in the top bits. Here too, under a hypervisor, it's all virtualized so qemu just gives 24 bit numbers to the various emulated MSIs as part of the global interrupt number space. I'm not sure how any of that would need kernel communication. All we need is to be able to associate a given global interrupt with an eventfd. I might just miss some subtleties here but so far I haven't been able to figure out how to "shoehorn" our stuff in the very x86-centric existing interfaces to the kernel APICs. In fact all that code is in a generic location in kvm but is really x86/ia64 centric and the interfaces seem to be as well. Cheers, Ben. -- 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
