On 06/14/2014 10:51 PM, Christoffer Dall wrote: > The VGIC virtual distributor implementation documentation was written a > very long time ago, before the true nature of the beast had been > partially absorbed into my bloodstream. I think this amalgamates the > two evil beings (myself and the code) a little more. > > Plus, it fixes an actual bug. ICFRn, pfff. > > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > --- > virt/kvm/arm/vgic.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c > index 1f91b3b..cc776af 100644 > --- a/virt/kvm/arm/vgic.c > +++ b/virt/kvm/arm/vgic.c > @@ -36,21 +36,22 @@ > * How the whole thing works (courtesy of Christoffer Dall): > * > * - At any time, the dist->irq_pending_on_cpu is the oracle that knows if > - * something is pending > - * - VGIC pending interrupts are stored on the vgic.irq_pending vgic > - * bitmap (this bitmap is updated by both user land ioctls and guest > - * mmio ops, and other in-kernel peripherals such as the > - * arch. timers) and indicate the 'wire' state. > + * something is pending on the CPU interface. > + * - Interrupts that are pending on the distributor are stored on the > + * vgic.irq_pending vgic bitmap (this bitmap is updated by both user land > + * ioctls and guest mmio ops, and other in-kernel peripherals such as the > + * arch. timers). ok forget my previous comment related to wire state;-) > * - Every time the bitmap changes, the irq_pending_on_cpu oracle is > * recalculated > * - To calculate the oracle, we need info for each cpu from > * compute_pending_for_cpu, which considers: > * - PPI: dist->irq_pending & dist->irq_enable > * - SPI: dist->irq_pending & dist->irq_enable & dist->irq_spi_target > - * - irq_spi_target is a 'formatted' version of the GICD_ICFGR > + * - irq_spi_target is a 'formatted' version of the GICD_ITARGETSRn > * registers, stored on each vcpu. We only keep one bit of > * information per interrupt, making sure that only one vcpu can > * accept the interrupt. > + * - If any of the above state changes, we must recalculate the oracle. > * - The same is true when injecting an interrupt, except that we only > * consider a single interrupt at a time. The irq_spi_cpu array > * contains the target CPU for each SPI. > -- 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
