Hi wanghaibin,
On 05/09/14 04:28, wanghaibin wrote:
> On 2014/8/21 21:06, Andre Przywara wrote:
>
>
>> +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;
>> +
>
>> + /*
>> + * 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
>
>> + 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) {
>
>> + 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.
>> + }
>> + /* 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);
>> +}
>> +
>> +
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