On Mon, Jun 08, 2015 at 06:03:57PM +0100, Marc Zyngier wrote:
> As we're about to introduce some serious GIC-poking to the vgic code,
> it is important to make sure that we're going to poke the part of
> the GIC that belongs to the CPU we're about to run on (otherwise,
> we'd end up with some unexpected interrupts firing)...
>
> Introducing a non-preemptible section in kvm_arch_vcpu_ioctl_run
> prevents the problem from occuring.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/kvm/arm.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 46db690..4986300 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -529,8 +529,18 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
> if (vcpu->arch.pause)
> vcpu_pause(vcpu);
>
> + /*
> + * Disarming the timer must be done with in a
s/with //
> + * preemptible context, as this call may sleep.
> + */
> kvm_timer_flush_hwstate(vcpu);
>
> + /*
> + * Preparing the interrupts to be injected also
> + * involves poking the GIC, which must be done in a
> + * non-preemptible context.
> + */
> + preempt_disable();
> kvm_vgic_flush_hwstate(vcpu);
>
> local_irq_disable();
> @@ -546,6 +556,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
> if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) {
> local_irq_enable();
> kvm_vgic_sync_hwstate(vcpu);
> + preempt_enable();
> kvm_timer_sync_hwstate(vcpu);
> continue;
> }
> @@ -580,6 +591,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>
> kvm_vgic_sync_hwstate(vcpu);
>
> + preempt_enable();
> +
> kvm_timer_sync_hwstate(vcpu);
>
> ret = handle_exit(vcpu, run, ret);
> --
> 2.1.4
>
This should get more simple when rebased on cpu time accounting patch,
but otherwise looks good.
-Christoffer
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