On Fri, Mar 14, 2014 at 02:40:22PM +0000, Marc Zyngier wrote:
> On Fri, Mar 14 2014 at 04:20:52 AM, Christoffer Dall <christoffer.dall@xxxxxxxxxx> wrote:
> > On Fri, Feb 14, 2014 at 02:28:06PM +0000, Marc Zyngier wrote:
> >> As it stands, nothing prevents userspace from injecting an interrupt
> >> before the guest's GIC is actually initialized.
> >>
> >> This goes unnoticed so far (as everything is pretty much statically
> >> allocated), but ends up exploding in a spectacular way once we switch
> >> to a more dynamic allocation (the GIC data structure isn't there yet).
> >>
> >> The fix is to test for the "ready" flag in the VGIC distributor before
> >> trying to inject the interrupt. Note that in order to avoid breaking
> >> userspace, we have to ignore what is essentially an error.
> >>
> >> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> >> ---
> >> virt/kvm/arm/vgic.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> >> index be456ce..d40fe61 100644
> >> --- a/virt/kvm/arm/vgic.c
> >> +++ b/virt/kvm/arm/vgic.c
> >> @@ -1386,7 +1386,8 @@ out:
> >> int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num,
> >> bool level)
> >> {
> >> - if (vgic_update_irq_state(kvm, cpuid, irq_num, level))
> >> + if (likely(vgic_initialized(kvm)) &&
> >
> > Do we need a barrier in kvm_vgic_init before setting the
> > kvm->arch.vgic.ready to ensure we observe the correctly initialized
> > values of the irq_spi_cpu field here?
>
> Ah, I see. Yes, possibly.
>
You can probably just mode the assignment of ready=true below the
critical section and you should be good, right?
Thanks,
-Christoffer
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