Messages in this thread | | | Subject | Re: [PATCH v3 29/32] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts | From | Zenghui Yu <> | Date | Wed, 15 Jan 2020 11:49:44 +0800 |
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Hi,
On 2020/1/15 10:49, 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> >> ---
[...]
>> 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. > >> + 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.
I think the thing is that we should _not_ try to configure vSGIs at all if kvm-arm.vgic_v4_enable=0 (which indicates we don't allow use of the GICv4 of direct injection).
We currently set kvm_vgic_global_state.has_gicv4_1 to true if HW support GICv4.1, regardless whatever the gicv4_enable is (see patch#23 - vgic_v3_probe). I think this is what actually needs fixing.
Thanks, Zenghui
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