Re: [Qemu-devel] [PATCH] RFCv3 kvm irqfd: support msimessage to irq translation in PHB

[Alexey Kardashevskiy]

Bring it up to support discussion in
[PATCH 0/2 v4] kvm irqfd: support msimessage to irq translation in PHB


On 06/30/2013 12:28 AM, Anthony Liguori wrote:
> On Sat, Jun 29, 2013 at 8:45 AM, Alexey Kardashevskiy <address@hidden> wrote:
>> On PPC64 systems MSI Messages are translated to system IRQ in a PCI
>> host bridge. This is already supported for emulated MSI/MSIX but
>> not for irqfd where the current QEMU allocates IRQ numbers from
>> irqchip and maps MSIMessages to those IRQ in the host kernel.
>>
>> The patch extends irqfd support in order to avoid unnecessary
>> mapping and reuse the one which already exists in a PCI host bridge.
>>
>> Specifically, a map_msi callback is added to PCIBus and pci_bus_map_msi()
>> to PCI API. The latter returns -1 if a specific PHB does not provide
>> with any trsnslation so the existing code will work.
> 
> I think there's a bit of confusion here.  The kernel needs a "virq"
> number to create an eventfd.  virq is just a KVM concept, it doesn't
> correspond to anything useful in hardware.
> 
> On pseries, there is a 1-1 mapping between XICS IRQs and VIRQs and MSI
> can be trivially mapped to a virq.
> 
> On x86, we need to call a special kernel function which essentially
> creates an apic message->virq mapping such that we can deliver the
> irqfd.
> 
> So what this should look like is:
> 
> 1) A PCI bus function to do the MSI -> virq mapping
> 2) On x86 (and e500), this is implemented by calling 
> kvm_irqchip_add_msi_route()
> 3) On pseries, this just returns msi->data
> 
> Perhaps (2) can just be the default PCI bus implementation to simplify things.
> 
>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>>
>> ---
>>
>> Looks like we agreed that in general PHB is the right place for this,
>> not KVM, so I am trying again.
>>
>> Probably something should be done to kvm_irqchip_update_msi_route()
>> as well but I do not really understand what exactly. Any suggestions?
>>
>>
>> ---
>>  hw/misc/vfio.c           |    7 +++++--
>>  hw/pci/pci.c             |   13 +++++++++++++
>>  hw/ppc/spapr_pci.c       |    6 ++++++
>>  hw/virtio/virtio-pci.c   |    2 +-
>>  include/hw/pci/pci.h     |    4 ++++
>>  include/hw/pci/pci_bus.h |    1 +
>>  include/sysemu/kvm.h     |    2 +-
>>  kvm-all.c                |    7 ++++++-
>>  8 files changed, 37 insertions(+), 5 deletions(-)
>>
>> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
>> index 52fb036..59911bb 100644
>> --- a/hw/misc/vfio.c
>> +++ b/hw/misc/vfio.c
>> @@ -624,7 +624,9 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, 
>> unsigned int nr,
>>       * Attempt to enable route through KVM irqchip,
>>       * default to userspace handling if unavailable.
>>       */
>> -    vector->virq = msg ? kvm_irqchip_add_msi_route(kvm_state, *msg) : -1;
>> +
>> +    vector->virq = msg ?
>> +            kvm_irqchip_add_msi_route(kvm_state, vdev->pdev.bus, *msg) : -1;
> 
> This is wrong.  You could call the bus function to map an MSI message
> to a virq here.
> 
>>      if (vector->virq < 0 ||
>>          kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
>>                                         vector->virq) < 0) {
>> @@ -792,7 +794,8 @@ retry:
>>           * Attempt to enable route through KVM irqchip,
>>           * default to userspace handling if unavailable.
>>           */
>> -        vector->virq = kvm_irqchip_add_msi_route(kvm_state, msg);
>> +        vector->virq = kvm_irqchip_add_msi_route(kvm_state, vdev->pdev.bus,
>> +                                                 msg);
> 
> And here.
> 
>>          if (vector->virq < 0 ||
>>              kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
>>                                             vector->virq) < 0) {
>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>> index 61b681a..543f172 100644
>> --- a/hw/pci/pci.c
>> +++ b/hw/pci/pci.c
>> @@ -1240,6 +1240,19 @@ void pci_device_set_intx_routing_notifier(PCIDevice 
>> *dev,
>>      dev->intx_routing_notifier = notifier;
>>  }
>>
>> +void pci_bus_set_map_msi_fn(PCIBus *bus, pci_map_msi_fn map_msi_fn)
>> +{
>> +    bus->map_msi = map_msi_fn;
>> +}
> 
> You don't need this function.  You can do this overloading as part of
> the PCI bus initialization in spapr_pci.c
> 
> Regards,
> 
> Anthony Liguori
> 
>> +int pci_bus_map_msi(PCIBus *bus, MSIMessage msg)
>> +{
>> +    if (bus->map_msi) {
>> +        return bus->map_msi(bus, msg);
>> +    }
>> +    return -1;
>> +}
>> +
>>  /*
>>   * PCI-to-PCI bridge specification
>>   * 9.1: Interrupt routing. Table 9-1
>> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
>> index 23dbc0e..bae4faf 100644
>> --- a/hw/ppc/spapr_pci.c
>> +++ b/hw/ppc/spapr_pci.c
>> @@ -486,6 +486,11 @@ static void spapr_msi_write(void *opaque, hwaddr addr,
>>      qemu_irq_pulse(xics_get_qirq(spapr->icp, irq));
>>  }
>>
>> +static int spapr_msi_get_irq(PCIBus *bus, MSIMessage msg)
>> +{
>> +    return msg.data;
>> +}
>> +
>>  static const MemoryRegionOps spapr_msi_ops = {
>>      /* There is no .read as the read result is undefined by PCI spec */
>>      .read = NULL,
>> @@ -657,6 +662,7 @@ static int spapr_phb_init(SysBusDevice *s)
>>
>>          sphb->lsi_table[i].irq = irq;
>>      }
>> +    pci_bus_set_map_msi_fn(bus, spapr_msi_get_irq);
>>
>>      return 0;
>>  }
>> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
>> index b070b64..06a4e13 100644
>> --- a/hw/virtio/virtio-pci.c
>> +++ b/hw/virtio/virtio-pci.c
>> @@ -481,7 +481,7 @@ static int kvm_virtio_pci_vq_vector_use(VirtIOPCIProxy 
>> *proxy,
>>      int ret;
>>
>>      if (irqfd->users == 0) {
>> -        ret = kvm_irqchip_add_msi_route(kvm_state, msg);
>> +        ret = kvm_irqchip_add_msi_route(kvm_state, proxy->pci_dev.bus, msg);
>>          if (ret < 0) {
>>              return ret;
>>          }
>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
>> index 6ef1f97..8c1edd6 100644
>> --- a/include/hw/pci/pci.h
>> +++ b/include/hw/pci/pci.h
>> @@ -332,6 +332,7 @@ MemoryRegion *pci_address_space_io(PCIDevice *dev);
>>  typedef void (*pci_set_irq_fn)(void *opaque, int irq_num, int level);
>>  typedef int (*pci_map_irq_fn)(PCIDevice *pci_dev, int irq_num);
>>  typedef PCIINTxRoute (*pci_route_irq_fn)(void *opaque, int pin);
>> +typedef int (*pci_map_msi_fn)(PCIBus *bus, MSIMessage msg);
>>
>>  typedef enum {
>>      PCI_HOTPLUG_DISABLED,
>> @@ -375,6 +376,9 @@ bool pci_intx_route_changed(PCIINTxRoute *old, 
>> PCIINTxRoute *new);
>>  void pci_bus_fire_intx_routing_notifier(PCIBus *bus);
>>  void pci_device_set_intx_routing_notifier(PCIDevice *dev,
>>                                            PCIINTxRoutingNotifier notifier);
>> +void pci_bus_set_map_msi_fn(PCIBus *bus, pci_map_msi_fn map_msi_fn);
>> +int pci_bus_map_msi(PCIBus *bus, MSIMessage msg);
>> +
>>  void pci_device_reset(PCIDevice *dev);
>>  void pci_bus_reset(PCIBus *bus);
>>
>> diff --git a/include/hw/pci/pci_bus.h b/include/hw/pci/pci_bus.h
>> index 66762f6..81efd2b 100644
>> --- a/include/hw/pci/pci_bus.h
>> +++ b/include/hw/pci/pci_bus.h
>> @@ -16,6 +16,7 @@ struct PCIBus {
>>      pci_set_irq_fn set_irq;
>>      pci_map_irq_fn map_irq;
>>      pci_route_irq_fn route_intx_to_irq;
>> +    pci_map_msi_fn map_msi;
>>      pci_hotplug_fn hotplug;
>>      DeviceState *hotplug_qdev;
>>      void *irq_opaque;
>> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
>> index f404d16..1bf2abe 100644
>> --- a/include/sysemu/kvm.h
>> +++ b/include/sysemu/kvm.h
>> @@ -305,8 +305,8 @@ static inline void cpu_synchronize_post_init(CPUState 
>> *cpu)
>>      }
>>  }
>>
>> -int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg);
>>  int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg);
>> +int kvm_irqchip_add_msi_route(KVMState *s, PCIBus *pbus, MSIMessage msg);
>>  void kvm_irqchip_release_virq(KVMState *s, int virq);
>>
>>  int kvm_irqchip_add_irqfd_notifier(KVMState *s, EventNotifier *n, int virq);
>> diff --git a/kvm-all.c b/kvm-all.c
>> index 1f81cca..3b7710d 100644
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
>> @@ -1180,11 +1180,16 @@ int kvm_irqchip_send_msi(KVMState *s, MSIMessage msg)
>>      return kvm_set_irq(s, route->kroute.gsi, 1);
>>  }
>>
>> -int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg)
>> +int kvm_irqchip_add_msi_route(KVMState *s, PCIBus *pbus, MSIMessage msg)
>>  {
>>      struct kvm_irq_routing_entry kroute;
>>      int virq;
>>
>> +    virq = pci_bus_map_msi(pbus, msg);
>> +    if (virq >= 0) {
>> +        return virq;
>> +    }
>> +
>>      if (!kvm_gsi_routing_enabled()) {
>>          return -ENOSYS;
>>      }
>> --
>> 1.7.10.4
>>
>>


-- 
Alexey