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authorChristoffer Dall <christoffer.dall@linaro.org>2017-09-14 11:08:45 -0700
committerChristoffer Dall <christoffer.dall@linaro.org>2018-01-02 10:05:45 +0100
commit6c1b7521f4a07cc63bbe2dfe290efed47cdb780a (patch)
tree13582e856147158b57fccd022e6e5f0b77dc2444 /virt
parent5a24575032971c5a9a4580417a791c427ebdb8e5 (diff)
downloadlinux-stericsson-6c1b7521f4a07cc63bbe2dfe290efed47cdb780a.tar.gz
KVM: arm/arm64: Factor out functionality to get vgic mmio requester_vcpu
We are about to distinguish between userspace accesses and mmio traps for a number of the mmio handlers. When the requester vcpu is NULL, it means we are handling a userspace access. Factor out the functionality to get the request vcpu into its own function, mostly so we have a common place to document the semantics of the return value. Also take the chance to move the functionality outside of holding a spinlock and instead explicitly disable and enable preemption. This supports PREEMPT_RT kernels as well. Acked-by: Marc Zyngier <marc.zyngier@arm.com> Reviewed-by: Andre Przywara <andre.przywara@arm.com> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/arm/vgic/vgic-mmio.c44
1 files changed, 28 insertions, 16 deletions
diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index deb51ee16a3d..fdad95f62fa3 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -122,6 +122,27 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
return value;
}
+/*
+ * This function will return the VCPU that performed the MMIO access and
+ * trapped from within the VM, and will return NULL if this is a userspace
+ * access.
+ *
+ * We can disable preemption locally around accessing the per-CPU variable,
+ * and use the resolved vcpu pointer after enabling preemption again, because
+ * even if the current thread is migrated to another CPU, reading the per-CPU
+ * value later will give us the same value as we update the per-CPU variable
+ * in the preempt notifier handlers.
+ */
+static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
+{
+ struct kvm_vcpu *vcpu;
+
+ preempt_disable();
+ vcpu = kvm_arm_get_running_vcpu();
+ preempt_enable();
+ return vcpu;
+}
+
void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
gpa_t addr, unsigned int len,
unsigned long val)
@@ -184,24 +205,10 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
bool new_active_state)
{
- struct kvm_vcpu *requester_vcpu;
unsigned long flags;
- spin_lock_irqsave(&irq->irq_lock, flags);
+ struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
- /*
- * The vcpu parameter here can mean multiple things depending on how
- * this function is called; when handling a trap from the kernel it
- * depends on the GIC version, and these functions are also called as
- * part of save/restore from userspace.
- *
- * Therefore, we have to figure out the requester in a reliable way.
- *
- * When accessing VGIC state from user space, the 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.
- */
- requester_vcpu = kvm_arm_get_running_vcpu();
+ spin_lock_irqsave(&irq->irq_lock, flags);
/*
* If this virtual IRQ was written into a list register, we
@@ -213,6 +220,11 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
* 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 */