Re: [Qemu-devel] [RFC][patch 0/6] pci pass-through support for qemu/KVM on s390

[Alex Williamson]

On Mon, 2014-09-08 at 11:20 +0200, Paolo Bonzini wrote:
> Il 06/09/2014 01:19, Alexander Graf ha scritto:
> >> > 1) interpretive execution of pci load/store instruction. If we use this 
> >> > function
> >> >    pci access does not get intercepted (no SIE exit) but is handled via 
> >> > microcode.
> >> >    To enable this we have to disable zpci device and enable it again 
> >> > with information
> >> >    from the SIE control block.
> > Hrm. So how about you create a special vm ioctl for KVM that allows you
> > to attach a VFIO device fd into the KVM VM context? Then the default
> > would stay "accessible by mmap traps", but we could accelerate it with KVM.
> 
> There is already KVM_DEV_VFIO_GROUP_ADD and KVM_DEV_VFIO_GROUP_DEL.
> 
> Right now, they result in a call to kvm_arch_register_noncoherent_dma or
> kvm_arch_unregister_noncoherent_dma, but you can add more hooks.

Eric Auger is also working on a patch series to do IRQ forward control
on ARM via the kvm-vfio pseudo device, extending the interface to
register VFIO device fds.  Sounds like that may be a good path to follow
here too.  Thanks,

Alex