Messages in this thread | | | Date | Wed, 15 Jan 2020 13:17:24 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH v3 29/32] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts |
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On 2020-01-15 02:49, Shaokun Zhang wrote: > Hi Marc, [This is from Nianyao] > > On 2019/12/24 19:10, Marc Zyngier wrote: >> In order to let a guest buy in the new, active-less SGIs, we >> need to be able to switch between the two modes. >> >> Handle this by stopping all guest activity, transfer the state >> from one mode to the other, and resume the guest. >> >> Signed-off-by: Marc Zyngier <maz@kernel.org> >> --- >> include/kvm/arm_vgic.h | 3 ++ >> virt/kvm/arm/vgic/vgic-v3.c | 2 + >> virt/kvm/arm/vgic/vgic-v4.c | 96 >> +++++++++++++++++++++++++++++++++++++ >> virt/kvm/arm/vgic/vgic.h | 1 + >> 4 files changed, 102 insertions(+) >> >> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h >> index 63457908c9c4..69f4164d6477 100644 >> --- a/include/kvm/arm_vgic.h >> +++ b/include/kvm/arm_vgic.h >> @@ -231,6 +231,9 @@ struct vgic_dist { >> /* distributor enabled */ >> bool enabled; >> >> + /* Wants SGIs without active state */ >> + bool nassgireq; >> + >> struct vgic_irq *spis; >> >> struct vgic_io_device dist_iodev; >> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c >> index c2fdea201747..c79a251c4974 100644 >> --- a/virt/kvm/arm/vgic/vgic-v3.c >> +++ b/virt/kvm/arm/vgic/vgic-v3.c >> @@ -540,6 +540,8 @@ int vgic_v3_map_resources(struct kvm *kvm) >> goto out; >> } >> >> + if (kvm_vgic_global_state.has_gicv4_1) >> + vgic_v4_configure_vsgis(kvm); >> dist->ready = true; >> >> out: >> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c >> index c2fcde104ea2..063785fd2dc7 100644 >> --- a/virt/kvm/arm/vgic/vgic-v4.c >> +++ b/virt/kvm/arm/vgic/vgic-v4.c >> @@ -97,6 +97,102 @@ static irqreturn_t vgic_v4_doorbell_handler(int >> irq, void *info) >> return IRQ_HANDLED; >> } >> >> +static void vgic_v4_sync_sgi_config(struct its_vpe *vpe, struct >> vgic_irq *irq) >> +{ >> + vpe->sgi_config[irq->intid].enabled = irq->enabled; >> + vpe->sgi_config[irq->intid].group = irq->group; >> + vpe->sgi_config[irq->intid].priority = irq->priority; >> +} >> + >> +static void vgic_v4_enable_vsgis(struct kvm_vcpu *vcpu) >> +{ >> + struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe; >> + int i; >> + >> + /* >> + * With GICv4.1, every virtual SGI can be directly injected. So >> + * let's pretend that they are HW interrupts, tied to a host >> + * IRQ. The SGI code will do its magic. >> + */ >> + for (i = 0; i < VGIC_NR_SGIS; i++) { >> + struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, i); >> + struct irq_desc *desc; >> + int ret; >> + >> + if (irq->hw) { >> + vgic_put_irq(vcpu->kvm, irq); >> + continue; >> + } >> + >> + irq->hw = true; >> + irq->host_irq = irq_find_mapping(vpe->sgi_domain, i); > > I think we need to check whether irq_find_mapping returns 0.
Why? its_alloc_vcpu_sgis() performs the allocation of all 16 SGIs in one go. If that fails, we should error out. Conversely, we're guaranteed that we have a mapping if it hasn't failed.
> >> + vgic_v4_sync_sgi_config(vpe, irq); >> + /* >> + * SGIs are initialised as disabled. Enable them if >> + * required by the rest of the VGIC init code. >> + */ >> + desc = irq_to_desc(irq->host_irq); >> + ret = irq_domain_activate_irq(irq_desc_get_irq_data(desc), >> + false); > > If irq->host_irq is not valid , in irq_domain_activate_irq, it will > trigger NULL pointer dereference in host kernel. > I meet a problem here. When hw support GIC4.1, and host kernel is > started with > kvm-arm.vgic_v4_enable=0, starting a virtual machine will trigger NULL > pointer > dereference in host. The following is error info:
[...]
But the problem here is that we're trying to use GICv4.1 even if GICv4 is disabled. I don't think there is a point in trying to sidestep this locally if we're doing the wrong thing at top-level, which seems to be the case.
Thanks,
M. -- Jazz is not dead. It just smells funny...
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