Re: [Qemu-devel] [RFC][PATCH 0/2] uq/master: Basic MSI support for in-kernel irqchip mode

[Michael S. Tsirkin]

On Wed, Mar 28, 2012 at 09:13:22AM +0200, Jan Kiszka wrote:
> On 2012-03-22 00:17, Jan Kiszka wrote:
> > Some half a year ago when I posted my first attempt to refactor MSI
> > for KVM support, we came to the conclusion that it might suffice to do
> > transparent dynamic routing for user-space injected MSI messages. These
> > two patches now implement such an approach for upstream.
> > 
> > As QEMU does not yet include irqfd support (for vhost) or pci device
> > assignment, this is already enough to enable MSI over the in-kernel
> > irqchip. Still, this is only RFC as it is just lightly tested and should
> > primarily collect feedback regarding the direction. If it's fine, I'd
> > like to base further qemu-kvm refactorings and upstream preparations on
> > top of such a series.
> > 
> > Also, I'd like to reanimate my KVM patch to provide direct MSI injection
> > in future kernels so that we do not need to take this long path here
> > forever.
> > 
> > Jan Kiszka (2):
> >   kvm: Introduce basic MSI support in-kernel irqchips
> >   KVM: x86: Wire up MSI support for in-kernel irqchip
> > 
> >  hw/apic.c     |    3 +
> >  hw/kvm/apic.c |   33 ++++++++++-
> >  hw/pc.c       |    5 --
> >  kvm-all.c     |  171 
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> >  kvm.h         |    1 +
> >  5 files changed, 205 insertions(+), 8 deletions(-)
> > 
> 
> Anyone any comments? I think this series could open the door for
> kernel_irqchip=on as default in QEMU 1.1.
> 
> Jan
> 

For what this patch is trying to do, would adding a simple ioctl for
injecting a given message into guest be cleaner?
Also, how would this support irqfd in the future? Will we have to
rip it all out and replace with per-device tracking that we
have today?

-- 
MST