On 05/04/17 10:28, Christoffer Dall wrote: > From: Alexander Graf <agraf@xxxxxxx> > > If you're running with a userspace gic or other interrupt constroller controller > (that is no vgic in the kernel), then you have so far not been able to > use the architected timers, because the output of the architected > timers, which are driven inside the kernel, was a kernel-only construct > between the arch timer code and the vgic. > > This patch implements the new KVM_CAP_ARM_USER_IRQ feature, where we use a > side channel on the kvm_run structure, run->s.regs.device_irq_level, to > always notify userspace of the timer output levels when using a userspace > irqchip. > > This works by ensureing that before we enter the guest, if the timer ensuring > output level has changed compared to what we last told userspace, we > don't enter the guest, but instead return to userspace to notify it of > the new level. If we are exiting, because of an MMIO for example, and > the level changed at the same time, the value is also updated and > userspace can sample the line as it needs. This is nicely achieved > simply always updating the timer_irq_level field after the main run > loop. > > Note that the kvm_timer_update_irq trace event is changed to show the > host IRQ number for the timer instead of the guest IRQ number, because > the kernel no longer know which IRQ userspace wires up the timer signal > to. > > Also note that this patch implements all required functionality but does > not yet advertise the capability. > > Signed-off-by: Alexander Graf <agraf@xxxxxxx> > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> Otherwise looks good. M. -- Jazz is not dead. It just smells funny...
