Re: [RFC PATCH 28/45] KVM: arm/arm64: vgic-new: Add GICv3 SGI system register trap handler

Christoffer Dall
2016-03-31T12:07:55Z

On Fri, Mar 25, 2016 at 02:04:51AM +0000, Andre Przywara wrote:
> In contrast to GICv2 SGIs in a GICv3 implementation are not triggered
> by a MMIO write, but with a system register write. KVM knows about
> that register already, we just need to implement the handler and wire
> it up to the core KVM/ARM code.
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> include/kvm/vgic/vgic.h | 8 ++++
> virt/kvm/arm/vgic/vgic_mmio.c | 101 ++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 109 insertions(+)
>
> diff --git a/include/kvm/vgic/vgic.h b/include/kvm/vgic/vgic.h
> index a8262c7..ab5fcc7 100644
> --- a/include/kvm/vgic/vgic.h
> +++ b/include/kvm/vgic/vgic.h
> @@ -202,6 +202,14 @@ bool kvm_vcpu_has_pending_irqs(struct kvm_vcpu *vcpu);
> void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu);
> void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu);
>
> +#ifdef CONFIG_KVM_ARM_VGIC_V3
> +void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg);
> +#else
> +static inline void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg)
> +{
> +}
> +#endif
> +
> /**
> * kvm_vgic_get_max_vcpus - Get the maximum number of VCPUs allowed by HW
> *
> diff --git a/virt/kvm/arm/vgic/vgic_mmio.c b/virt/kvm/arm/vgic/vgic_mmio.c
> index 44fdba5..7eb6b93 100644
> --- a/virt/kvm/arm/vgic/vgic_mmio.c
> +++ b/virt/kvm/arm/vgic/vgic_mmio.c
> @@ -1139,4 +1139,105 @@ int vgic_register_redist_regions(struct kvm *kvm, gpa_t redist_base_address)
>
> return ret;
> }
> +
> +/*
> + * Compare a given affinity (level 1-3 and a level 0 mask, from the SGI
> + * generation register ICC_SGI1R_EL1) with a given VCPU.
> + * If the VCPU's MPIDR matches, return the level0 affinity, otherwise
> + * return -1.
> + */
> +static int match_mpidr(u64 sgi_aff, u16 sgi_cpu_mask, struct kvm_vcpu *vcpu)
> +{
> + unsigned long affinity;
> + int level0;
> +
> + /*
> + * Split the current VCPU's MPIDR into affinity level 0 and the
> + * rest as this is what we have to compare against.
> + */
> + affinity = kvm_vcpu_get_mpidr_aff(vcpu);
> + level0 = MPIDR_AFFINITY_LEVEL(affinity, 0);
> + affinity &= ~MPIDR_LEVEL_MASK;
> +
> + /* bail out if the upper three levels don't match */
> + if (sgi_aff != affinity)
> + return -1;
> +
> + /* Is this VCPU's bit set in the mask ? */
> + if (!(sgi_cpu_mask & BIT(level0)))
> + return -1;
> +
> + return level0;
> +}
> +
> +#define SGI_AFFINITY_LEVEL(reg, level) \
> + ((((reg) & ICC_SGI1R_AFFINITY_## level ##_MASK) \
> + >> ICC_SGI1R_AFFINITY_## level ##_SHIFT) << MPIDR_LEVEL_SHIFT(level))

wholy crap? What is this? Yikes, this is already in the kernel. Oh
well, I'm not going to try to understand it again then.

> +
> +/**
> + * vgic_v3_dispatch_sgi - handle SGI requests from VCPUs
> + * @vcpu: The VCPU requesting a SGI
> + * @reg: The value written into the ICC_SGI1R_EL1 register by that VCPU
> + *
> + * With GICv3 (and ARE=1) CPUs trigger SGIs by writing to a system register.
> + * This will trap in sys_regs.c and call this function.
> + * This ICC_SGI1R_EL1 register contains the upper three affinity levels of the
> + * target processors as well as a bitmask of 16 Aff0 CPUs.
> + * If the interrupt routing mode bit is not set, we iterate over all VCPUs to
> + * check for matching ones. If this bit is set, we signal all, but not the
> + * calling VCPU.
> + */
> +void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg)
> +{
> + struct kvm *kvm = vcpu->kvm;
> + struct kvm_vcpu *c_vcpu;
> + u16 target_cpus;
> + u64 mpidr;
> + int sgi, c;
> + int vcpu_id = vcpu->vcpu_id;
> + bool broadcast;
> +
> + sgi = (reg & ICC_SGI1R_SGI_ID_MASK) >> ICC_SGI1R_SGI_ID_SHIFT;
> + broadcast = reg & BIT(ICC_SGI1R_IRQ_ROUTING_MODE_BIT);
> + target_cpus = (reg & ICC_SGI1R_TARGET_LIST_MASK) >> ICC_SGI1R_TARGET_LIST_SHIFT;
> + mpidr = SGI_AFFINITY_LEVEL(reg, 3);
> + mpidr |= SGI_AFFINITY_LEVEL(reg, 2);
> + mpidr |= SGI_AFFINITY_LEVEL(reg, 1);
> +
> + /*
> + * We iterate over all VCPUs to find the MPIDRs matching the request.
> + * If we have handled one CPU, we clear it's bit to detect early

s/it's/its/

> + * if we are already finished. This avoids iterating through all
> + * VCPUs when most of the times we just signal a single VCPU.
> + */
> + kvm_for_each_vcpu(c, c_vcpu, kvm) {
> + struct vgic_irq *irq;
> +
> + /* Exit early if we have dealt with all requested CPUs */
> + if (!broadcast && target_cpus == 0)
> + break;
> +
> + /* Don't signal the calling VCPU */
> + if (broadcast && c == vcpu_id)
> + continue;
> +
> + if (!broadcast) {
> + int level0;
> +
> + level0 = match_mpidr(mpidr, target_cpus, c_vcpu);
> + if (level0 == -1)
> + continue;
> +
> + /* remove this matching VCPU from the mask */
> + target_cpus &= ~BIT(level0);
> + }
> +
> + irq = vgic_get_irq(vcpu->kvm, c_vcpu, sgi);
> +
> + spin_lock(&irq->irq_lock);
> + irq->pending = true;
> +
> + vgic_queue_irq(vcpu->kvm, irq);
> + }

eventually I suspect we should implement a linear time 'give me a vcpu
based on this mpidr' lookup function, but this should be fine for now.

> +}
> #endif
> --
> 2.7.3
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html