diff mbox series

[08/37] KVM: arm/arm64: Fix vgic init race

Message ID 20180813145755.16566-9-marc.zyngier@arm.com (mailing list archive)
State New, archived
Headers show
Series [01/37] arm64: KVM: Add support for Stage-2 control of memory types and cacheability | expand

Commit Message

Marc Zyngier Aug. 13, 2018, 2:57 p.m. UTC 
From: Christoffer Dall <christoffer.dall@arm.com>

The vgic_init function can race with kvm_arch_vcpu_create() which does
not hold kvm_lock() and we therefore have no synchronization primitives
to ensure we're doing the right thing.

As the user is trying to initialize or run the VM while at the same time
creating more VCPUs, we just have to refuse to initialize the VGIC in
this case rather than silently failing with a broken VCPU.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 virt/kvm/arm/vgic/vgic-init.c | 4 ++++
 1 file changed, 4 insertions(+)
diff mbox series

Patch

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 2673efce65f3..b71417913741 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -271,6 +271,10 @@  int vgic_init(struct kvm *kvm)
 	if (vgic_initialized(kvm))
 		return 0;
 
+	/* Are we also in the middle of creating a VCPU? */
+	if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
+		return -EBUSY;
+
 	/* freeze the number of spis */
 	if (!dist->nr_spis)
 		dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;