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
