Hi wanghaibin,

On 05/09/14 04:28, wanghaibin wrote:

On 2014/8/21 21:06, Andre Przywara wrote:

quoted

+void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg)
+{
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_vcpu *c_vcpu;
+	struct vgic_dist *dist = &kvm->arch.vgic;
+	u16 target_cpus;
+	u64 mpidr, mpidr_h, mpidr_l;
+	int sgi, mode, c, vcpu_id;
+	int updated = 0;
+
+	vcpu_id = vcpu->vcpu_id;
+
+	sgi = (reg >> 24) & 0xf;
+	mode = (reg >> 40) & 0x1;
+	target_cpus = reg & 0xffff;
+	mpidr = ((reg >> 48) & 0xff) << MPIDR_LEVEL_SHIFT(3);
+	mpidr |= ((reg >> 32) & 0xff) << MPIDR_LEVEL_SHIFT(2);
+	mpidr |= ((reg >> 16) & 0xff) << MPIDR_LEVEL_SHIFT(1);
+	mpidr &= ~MPIDR_LEVEL_MASK;
+

quoted

+	/*
+	 * We take the dist lock here, because we come from the sysregs
+	 * code path and not from MMIO (where this is already done)
+	 */
+	spin_lock(&dist->lock);
+	kvm_for_each_vcpu(c, c_vcpu, kvm) {

Hi, Andre, there is a suggestion. Move the

quoted

+		if (target_cpus == 0)
+			break;

code, out the  kvm_for_each_vcpu loop, Like :


	if (!mode && target_cpus == 0)   /* the judgement do not need judge in kvm_for_each_vcpu loop */
		return;

I am not so much concerned about someone actually sending a SGI to
no-one, but the code is there to stop the loop after the only CPU has
been serviced.
...

	spin_lock(&dist->lock);
	kvm_for_each_vcpu(c, c_vcpu, kvm) {

quoted

+		if (mode && c == vcpu_id)       /* not to myself */
+			continue;
+		if (!mode) {
+			mpidr_h = kvm_vcpu_get_mpidr(c_vcpu);
+			mpidr_l = MPIDR_AFFINITY_LEVEL(mpidr_h, 0);
+			mpidr_h &= ~MPIDR_LEVEL_MASK;
+			if (mpidr != mpidr_h)
+				continue;
+			if (!(target_cpus & BIT(mpidr_l)))
+				continue;
+			target_cpus &= ~BIT(mpidr_l);

Here the CPU bit is removed from target_cpus. The idea is that most of
the time we trigger a SGI for a single CPU only, so there is no need to
further iterate through all VCPUs once we found the first and only one.
That's why I check target_cpus inside the loop.

Regards,
Andre.

quoted

+		}
+		/* Flag the SGI as pending */
+		vgic_dist_irq_set(c_vcpu, sgi);
+		updated = 1;
+		kvm_debug("SGI%d from CPU%d to CPU%d\n", sgi, vcpu_id, c);
+	}
+	if (updated)
+		vgic_update_state(vcpu->kvm);
+	spin_unlock(&dist->lock);
+	if (updated)
+		vgic_kick_vcpus(vcpu->kvm);
+}
+
+