On Tue, Dec 19, 2017 at 02:17:38PM +0000, Julien Thierry wrote: > Hi Christoffer, > > A few nits in the commit message. > > On 13/12/17 10:45, Christoffer Dall wrote: > >The timer was modeled after a strict idea of modelling an interrupt line > > nit: modelling (also, modeled after a strict idea of modelling?) > Yes, I model the modelling of models of modeled timers. Is that not clear? ;) > >level in software, meaning that only transitions in the level needed to > > s/needed/need/ ? > ack > >be reported to the VGIC. This works well for the timer, because the > >arch timer code is in complete control of the device and can track the > >transitions of the line. > > > >However, as we are about to support using the HW bit in the VGIC not > >just for the timer, but also for VFIO which cannot track transitions of > >the interrupt line, we have to decide on an interface for level > >triggered mapped interrupts to the GIC, which both the timer and VFIO > > "level triggered interrupts mapped to the GIC" ? > an interface to the GIC for level ... My writing here is really crap. Thanks for pointing that out. > >can use. > > > >VFIO only sees an asserting transition of the physical interrupt line, > >and tells the VGIC when that happens. That means that part of the > >interrupt flow is offloaded to the hardware. > > > >To use the same interface for VFIO devices and the timer, we therefore > >have to change the timer (we cannot change VFIO because it doesn't know > >the details of the device it is assigning to a VM). > > > >Luckily, changing the timer is simple, we just need to stop 'caching' > >the line level, but instead let the VGIC know the state of the timer > >every time there is a potential change in the line level, and when the > >line level should be asserted from the timer ISR. The VGIC can ignore > >extra notifications using its validate mechanism. > > > >Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx> > >Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > > Reviewed-by: Julien Thierry <julien.thierry@xxxxxxx> > Thanks, -Christoffer
