Messages in this thread | | | Subject | Re: [PATCH v5 20/23] KVM: arm64: GICv4.1: Plumb SGI implementation selection in the distributor | From | Zenghui Yu <> | Date | Fri, 20 Mar 2020 11:08:39 +0800 |
| |
On 2020/3/20 4:38, Auger Eric wrote: > Hi Marc, > On 3/19/20 1:10 PM, Marc Zyngier wrote: >> Hi Zenghui, >> >> On 2020-03-18 06:34, Zenghui Yu wrote: >>> Hi Marc, >>> >>> On 2020/3/5 4:33, Marc Zyngier wrote: >>>> The GICv4.1 architecture gives the hypervisor the option to let >>>> the guest choose whether it wants the good old SGIs with an >>>> active state, or the new, HW-based ones that do not have one. >>>> >>>> For this, plumb the configuration of SGIs into the GICv3 MMIO >>>> handling, present the GICD_TYPER2.nASSGIcap to the guest, >>>> and handle the GICD_CTLR.nASSGIreq setting. >>>> >>>> In order to be able to deal with the restore of a guest, also >>>> apply the GICD_CTLR.nASSGIreq setting at first run so that we >>>> can move the restored SGIs to the HW if that's what the guest >>>> had selected in a previous life. >>> >>> I'm okay with the restore path. But it seems that we still fail to >>> save the pending state of vSGI - software pending_latch of HW-based >>> vSGIs will not be updated (and always be false) because we directly >>> inject them through ITS, so vgic_v3_uaccess_read_pending() can't >>> tell the correct pending state to user-space (the correct one should >>> be latched in HW). >>> >>> It would be good if we can sync the hardware state into pending_latch >>> at an appropriate time (just before save), but not sure if we can... >> >> The problem is to find the "appropriate time". It would require to define >> a point in the save sequence where we transition the state from HW to >> SW. I'm not keen on adding more state than we already have. > > may be we could use a dedicated device group/attr as we have for the ITS > save tables? the user space would choose.
It means that userspace will be aware of some form of GICv4.1 details (e.g., get/set vSGI state at HW level) that KVM has implemented. Is it something that userspace required to know? I'm open to this ;-)
> > Thanks > > Eric >> >> But what we can do is to just ask the HW to give us the right state >> on userspace access, at all times. How about this: >> >> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c >> b/virt/kvm/arm/vgic/vgic-mmio-v3.c >> index 48fd9fc229a2..281fe7216c59 100644 >> --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c >> +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c >> @@ -305,8 +305,18 @@ static unsigned long >> vgic_v3_uaccess_read_pending(struct kvm_vcpu *vcpu, >> */ >> for (i = 0; i < len * 8; i++) { >> struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i); >> + bool state = irq->pending_latch; >> >> - if (irq->pending_latch) >> + if (irq->hw && vgic_irq_is_sgi(irq->intid)) { >> + int err; >> + >> + err = irq_get_irqchip_state(irq->host_irq, >> + IRQCHIP_STATE_PENDING, >> + &state); >> + WARN_ON(err); >> + } >> + >> + if (state) >> value |= (1U << i); >> >> vgic_put_irq(vcpu->kvm, irq);
Anyway this looks good to me and will do the right thing on a userspace save.
>> >> I can add this to "KVM: arm64: GICv4.1: Add direct injection capability >> to SGI registers".
Thanks, Zenghui
| |