[v2,02/10] arm/arm64: KVM: Move vgic handling to a non-preemptible section
diff mbox

Message ID 1436378202-20224-3-git-send-email-marc.zyngier@arm.com
State New
Headers show

Commit Message

Marc Zyngier July 8, 2015, 5:56 p.m. UTC
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@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
---
 arch/arm/kvm/arm.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Comments

Christoffer Dall July 17, 2015, 10:15 p.m. UTC | #1
On Wed, Jul 08, 2015 at 06:56:34PM +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@arm.com>
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
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Patch
diff mbox

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index d605180..1583a34 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -528,10 +528,20 @@  int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		if (vcpu->arch.pause)
 			vcpu_pause(vcpu);
 
+		/*
+		 * Disarming the background timer must be done in a
+		 * preemptible context, as this call may sleep.
+		 */
 		kvm_timer_flush_hwstate(vcpu);
-		kvm_vgic_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();
 
 		/*
@@ -544,8 +554,8 @@  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();
-			preempt_enable();
 			kvm_vgic_sync_hwstate(vcpu);
+			preempt_enable();
 			kvm_timer_sync_hwstate(vcpu);
 			continue;
 		}
@@ -586,9 +596,11 @@  int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		 */
 		kvm_guest_exit();
 		trace_kvm_exit(kvm_vcpu_trap_get_class(vcpu), *vcpu_pc(vcpu));
-		preempt_enable();
 
 		kvm_vgic_sync_hwstate(vcpu);
+
+		preempt_enable();
+
 		kvm_timer_sync_hwstate(vcpu);
 
 		ret = handle_exit(vcpu, run, ret);