Re: [PATCH 41/55] KVM: arm64: vgic-its: Implement MSI injection in ITS emulation

Marc Zyngier
2016-08-02T10:18:03Z

On 01/08/16 19:20, Christoffer Dall wrote:
> On Fri, Jul 22, 2016 at 06:28:58PM +0100, Marc Zyngier wrote:
>> From: Andre Przywara <andre.przywara@arm.com>
>>
>> When userland wants to inject an MSI into the guest, it uses the
>> KVM_SIGNAL_MSI ioctl, which carries the doorbell address along with
>> the payload and the device ID.
>> With the help of the KVM IO bus framework we learn the corresponding
>> ITS from the doorbell address. We then use our wrapper functions to
>> iterate the linked lists and find the proper Interrupt Translation Table
>> Entry (ITTE) and thus the corresponding struct vgic_irq to finally set
>> the pending bit.
>> We also provide the handler for the ITS "INT" command, which allows a
>> guest to trigger an MSI via the ITS command queue. Since this one knows
>> about the right ITS already, we directly call the MMIO handler function
>> without using the kvm_io_bus framework.
>>
>> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
>> Tested-by: Eric Auger <eric.auger@redhat.com>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>> virt/kvm/arm/vgic/vgic-its.c | 77 ++++++++++++++++++++++++++++++++++++++++++++
>> virt/kvm/arm/vgic/vgic.h | 6 ++++
>> 2 files changed, 83 insertions(+)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>> index 1408c88..d8e8f14 100644
>> --- a/virt/kvm/arm/vgic/vgic-its.c
>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>> @@ -437,6 +437,65 @@ static unsigned long vgic_mmio_read_its_idregs(struct kvm *kvm,
>> return 0;
>> }
>>
>> +/*
>> + * Find the target VCPU and the LPI number for a given devid/eventid pair
>> + * and make this IRQ pending, possibly injecting it.
>> + * Must be called with the its_lock mutex held.
>> + */
>> +static void vgic_its_trigger_msi(struct kvm *kvm, struct vgic_its *its,
>> + u32 devid, u32 eventid)
>> +{
>> + struct its_itte *itte;
>> +
>> + if (!its->enabled)
>> + return;
>> +
>> + itte = find_itte(its, devid, eventid);
>> + /* Triggering an unmapped IRQ gets silently dropped. */
>> + if (itte && its_is_collection_mapped(itte->collection)) {
>> + struct kvm_vcpu *vcpu;
>> +
>> + vcpu = kvm_get_vcpu(kvm, itte->collection->target_addr);
>> + if (vcpu && vcpu->arch.vgic_cpu.lpis_enabled) {
>> + spin_lock(&itte->irq->irq_lock);
>> + itte->irq->pending = true;
>> + vgic_queue_irq_unlock(kvm, itte->irq);
>> + }
>> + }
>> +}
>> +
>> +/*
>> + * Queries the KVM IO bus framework to get the ITS pointer from the given
>> + * doorbell address.
>> + * We then call vgic_its_trigger_msi() with the decoded data.
>> + */
>> +int vgic_its_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
>> +{
>> + u64 address;
>> + struct kvm_io_device *kvm_io_dev;
>> + struct vgic_io_device *iodev;
>> +
>> + if (!vgic_has_its(kvm))
>> + return -ENODEV;
>> +
>> + if (!(msi->flags & KVM_MSI_VALID_DEVID))
>> + return -EINVAL;
>> +
>> + address = (u64)msi->address_hi << 32 | msi->address_lo;
>> +
>> + kvm_io_dev = kvm_io_bus_get_dev(kvm, KVM_MMIO_BUS, address);
>> + if (!kvm_io_dev)
>> + return -ENODEV;
>> +
>> + iodev = container_of(kvm_io_dev, struct vgic_io_device, dev);
>> +
>> + mutex_lock(&iodev->its->its_lock);
>> + vgic_its_trigger_msi(kvm, iodev->its, msi->devid, msi->data);
>> + mutex_unlock(&iodev->its->its_lock);
>> +
>> + return 0;
>
> According to KVM_SIGNAL_MSI this means that the guest blocked the MSI.
> Is this the intention, or is the return value translated somewhere
> higher in the call stack?

I'm afraid it is not, and this is definitely a bug. Andre, can you
please address this one urgently, as this has a direct impact on the
userspace API?

Thanks,

M.
--
Jazz is not dead. It just smells funny...