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KVM: arm/arm64: vgic: Do not cond_resched_lock() with IRQs disabled

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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>
This commit is contained in:
Julien Thierry 2018-11-26 18:26:44 +00:00 committed by Marc Zyngier
parent b8e0ba7c8b
commit 2e2f6c3c0b
1 changed files with 0 additions and 21 deletions
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21
virt/kvm/arm/vgic/vgic-mmio.c
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@ -313,27 +313,6 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
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 {