4.20-stable review patch. If anyone has any objections, please let me know.
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From: Julien Thierry julien.thierry@arm.com
commit 2e2f6c3c0b08eed3fcf7de3c7684c940451bdeb1 upstream.
To change the active state of an MMIO, halt is requested for all vcpus of the affected guest before modifying the IRQ state. This is done by calling cond_resched_lock() in vgic_mmio_change_active(). However interrupts are disabled at this point and we cannot reschedule a vcpu.
We actually don't need any of this, as kvm_arm_halt_guest ensures that all the other vcpus are out of the guest. Let's just drop that useless code.
Signed-off-by: Julien Thierry julien.thierry@arm.com Suggested-by: Christoffer Dall christoffer.dall@arm.com Cc: stable@vger.kernel.org Signed-off-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- virt/kvm/arm/vgic/vgic-mmio.c | 21 --------------------- 1 file changed, 21 deletions(-)
--- a/virt/kvm/arm/vgic/vgic-mmio.c +++ b/virt/kvm/arm/vgic/vgic-mmio.c @@ -313,27 +313,6 @@ static void vgic_mmio_change_active(stru
spin_lock_irqsave(&irq->irq_lock, flags);
- /* - * If this virtual IRQ was written into a list register, we - * have to make sure the CPU that runs the VCPU thread has - * synced back the LR state to the struct vgic_irq. - * - * As long as the conditions below are true, we know the VCPU thread - * may be on its way back from the guest (we kicked the VCPU thread in - * vgic_change_active_prepare) and still has to sync back this IRQ, - * so we release and re-acquire the spin_lock to let the other thread - * sync back the IRQ. - * - * When accessing VGIC state from user space, requester_vcpu is - * NULL, which is fine, because we guarantee that no VCPUs are running - * when accessing VGIC state from user space so irq->vcpu->cpu is - * always -1. - */ - while (irq->vcpu && /* IRQ may have state in an LR somewhere */ - irq->vcpu != requester_vcpu && /* Current thread is not the VCPU thread */ - irq->vcpu->cpu != -1) /* VCPU thread is running */ - cond_resched_lock(&irq->irq_lock); - if (irq->hw) { vgic_hw_irq_change_active(vcpu, irq, active, !requester_vcpu); } else {