[PATCH 4/5] KVM: arm64: vgic-v3: Refactor GICv3 SGI generation
Zenghui Yu
zenghui.yu at linux.dev
Sun Sep 10 09:25:36 PDT 2023
Hi Marc,
On 2023/9/7 18:09, Marc Zyngier wrote:
> As we're about to change the way SGIs are sent, start by splitting
> out some of the basic functionnality: instead of intermingling
functionality
> the broadcast and non-broadcast cases with the actual SGI generation,
> perform the following cleanups:
>
> - move the SGI queuing into its own helper
> - split the broadcast code from the affinity-driven code
> - replace the mask/shift combinations with FIELD_GET()
>
> The result is much more readable, and paves the way for further
> optimisations.
Indeed!
> @@ -1070,19 +1102,30 @@ void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg, bool allow_group1)
> {
> struct kvm *kvm = vcpu->kvm;
> struct kvm_vcpu *c_vcpu;
> - u16 target_cpus;
> + unsigned long target_cpus;
> u64 mpidr;
> - int sgi;
> - int vcpu_id = vcpu->vcpu_id;
> - bool broadcast;
> - unsigned long c, flags;
> -
> - sgi = (reg & ICC_SGI1R_SGI_ID_MASK) >> ICC_SGI1R_SGI_ID_SHIFT;
> - broadcast = reg & BIT_ULL(ICC_SGI1R_IRQ_ROUTING_MODE_BIT);
> - target_cpus = (reg & ICC_SGI1R_TARGET_LIST_MASK) >> ICC_SGI1R_TARGET_LIST_SHIFT;
> + u32 sgi;
> + unsigned long c;
> +
> + sgi = FIELD_GET(ICC_SGI1R_SGI_ID_MASK, reg);
> +
> + /* Broadcast */
> + if (unlikely(reg & BIT_ULL(ICC_SGI1R_IRQ_ROUTING_MODE_BIT))) {
> + kvm_for_each_vcpu(c, c_vcpu, kvm) {
> + /* Don't signal the calling VCPU */
> + if (c_vcpu == vcpu)
> + continue;
> +
> + vgic_v3_queue_sgi(c_vcpu, sgi, allow_group1);
> + }
> +
> + return;
> + }
> +
> mpidr = SGI_AFFINITY_LEVEL(reg, 3);
> mpidr |= SGI_AFFINITY_LEVEL(reg, 2);
> mpidr |= SGI_AFFINITY_LEVEL(reg, 1);
> + target_cpus = FIELD_GET(ICC_SGI1R_TARGET_LIST_MASK, reg);
>
> /*
> * We iterate over all VCPUs to find the MPIDRs matching the request.
> @@ -1091,54 +1134,19 @@ void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg, bool allow_group1)
> * VCPUs when most of the times we just signal a single VCPU.
> */
> kvm_for_each_vcpu(c, c_vcpu, kvm) {
> - struct vgic_irq *irq;
> + int level0;
>
> /* Exit early if we have dealt with all requested CPUs */
> - if (!broadcast && target_cpus == 0)
> + if (target_cpus == 0)
> break;
> -
> - /* Don't signal the calling VCPU */
> - if (broadcast && c == vcpu_id)
Unrelated to this patch, but it looks that we were comparing the value
of *vcpu_idx* and vcpu_id to skip the calling VCPU. Is there a rule in
KVM that userspace should invoke KVM_CREATE_VCPU with sequential
"vcpu id"s, starting at 0, so that the user-provided vcpu_id always
equals to the KVM-internal vcpu_idx for a given VCPU?
I asked because it seems that in kvm/arm64 we always use
kvm_get_vcpu(kvm, i) to obtain the kvm_vcpu pointer, even if *i* is
sometimes essentially provided by userspace..
Besides, the refactor itself looks good to me.
Thanks,
Zenghui
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