Hi all,
On 07/06/2015 03:32 PM, Pavel Fedin wrote:
> Hi!
>
>>> Well, as we are about to implement this: yes. But the issue is that MSI
>>> injection and GSI routing code is generic PCI code in userland (at least
>>> in kvmtool, guess in QEMU, too), so I don't want to pull in any kind of
>>> ARM specific code in there. The idea is to always provide the device ID
>>> from the PCI code (for PCI devices it's just the B/D/F triplet), but
>>> only send it to the kernel if needed. Querying a KVM capability is
>>> perfectly fine for this IMO.
>>
>> Yes, I agree.
>
> Actually, we already have this capability, it's KVM_CAP_IRQ_ROUTING. If we have this capability,
> and want to use irqfds with GICv3, we need to set KVM_MSI_VALID_DEVID. And there is no other way to
> use irqfds with GICv3.
> Just for example, this is what i have done in qemu:
> --- cut ---
> int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg, PCIDevice *dev)
> {
> struct kvm_irq_routing_entry kroute = {};
> int virq;
>
> if (kvm_gsi_direct_mapping()) {
> return kvm_arch_msi_data_to_gsi(msg.data);
> }
>
> if (!kvm_gsi_routing_enabled()) {
> return -ENOSYS;
> }
>
> virq = kvm_irqchip_get_virq(s);
> if (virq < 0) {
> return virq;
> }
>
> kroute.gsi = virq;
> kroute.type = KVM_IRQ_ROUTING_MSI;
> kroute.u.msi.address_lo = (uint32_t)msg.address;
> kroute.u.msi.address_hi = msg.address >> 32;
> kroute.u.msi.data = le32_to_cpu(msg.data);
> kroute.flags = kvm_msi_flags;
> if (kroute.flags & KVM_MSI_VALID_DEVID) {
> kroute.u.msi.devid = (pci_bus_num(dev->bus) << 8) | dev->devfn;
> }
>
> if (kvm_arch_fixup_msi_route(&kroute, msg.address, msg.data)) {
> kvm_irqchip_release_virq(s, virq);
> return -EINVAL;
> }
>
> kvm_add_routing_entry(s, &kroute);
> kvm_irqchip_commit_routes(s);
>
> return virq;
> }
> --- cut ---
>
> ITS code in qemu just does:
>
> ---cut ---
> msi_supported = true;
> kvm_msi_flags = KVM_MSI_VALID_DEVID;
> kvm_msi_via_irqfd_allowed = kvm_has_gsi_routing();
> kvm_gsi_routing_allowed = kvm_msi_via_irqfd_allowed;
> --- cut ---
>
> I set KVM_MSI_VALID_DEVID unconditionally here just because it will never be checked if
> kvm_msi_via_irqfd_allowed is false, it's just qemu specifics. The more canonical form would perhaps
> be:
> --- cut ---
> if (kvm_has_gsi_routing()) {
> kvm_msi_flags = KVM_MSI_VALID_DEVID;
Personally I prefer a capability rather than hardcoding a global
variable value in the qemu interrupt controller code. All the more so
typically there is KVM GSI routing cap that could/should? be queried
instead of hardcoding the value I think.
So not sure whether we eventually concluded;-)
- introduce a KVM_CAP_MSI_DEVID capability? All OK except Pavel not
convinced?
- userspaces puts the devid in struct kvm_irq_routing_msi pad field:
consensus (we do not intrduce a new kvm_irq_routing_ext_msi)
- userspace tells it conveyed a devid by setting
A) the kvm_irq_routing_entry's field?
B) the kvm_irq_routing_entry's type
no consensus. If there is a cap, does it really matter?
Best Regards
Eric
> kvm_gsi_routing_allowed = true;
> kvm_msi_via_irqfd_allowed = true;
> }
> --- cut ---
>
> I can post my sets as RFCs to qemu mailing list, if you want to take a look at the whole change
> set.
>
> Kind regards,
> Pavel Fedin
> Expert Engineer
> Samsung Electronics Research center Russia
>
>
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