• Christoffer Dall's avatar
    KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs · df635c5b
    Christoffer Dall authored
    For mapped IRQs (with the HW bit set in the LR) we have to follow some
    rules of the architecture.  One of these rules is that VM must not be
    allowed to deactivate a virtual interrupt with the HW bit set unless the
    physical interrupt is also active.
    
    This works fine when injecting mapped interrupts, because we leave it up
    to the injector to either set EOImode==1 or manually set the active
    state of the physical interrupt.
    
    However, the guest can set virtual interrupt to be pending or active by
    writing to the virtual distributor, which could lead to deactivating a
    virtual interrupt with the HW bit set without the physical interrupt
    being active.
    
    We could set the physical interrupt to active whenever we are about to
    enter the VM with a HW interrupt either pending or active, but that
    would be really slow, especially on GICv2.  So we take the long way
    around and do the hard work when needed, which is expected to be
    extremely rare.
    
    When the VM sets the pending state for a HW interrupt on the virtual
    distributor we set the active state on the physical distributor, because
    the virtual interrupt can become active and then the guest can
    deactivate it.
    
    When the VM clears the pending state we also clear it on the physical
    side, because the injector might otherwise raise the interrupt.  We also
    clear the physical active state when the virtual interrupt is not
    active, since otherwise a SPEND/CPEND sequence from the guest would
    prevent signaling of future interrupts.
    
    Changing the state of mapped interrupts from userspace is not supported,
    and it's expected that userspace unmaps devices from VFIO before
    attempting to set the interrupt state, because the interrupt state is
    driven by hardware.
    Reviewed-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
    Reviewed-by: default avatarEric Auger <eric.auger@redhat.com>
    Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
    df635c5b
vgic.h 9.33 KB