Re: [Qemu-devel] [PATCH] RFC kvm irqfd: add directly mapped MSI IRQ support

[Anthony Liguori]

On Thu, Jun 20, 2013 at 11:46 PM, Alex Williamson
<address@hidden> wrote:
> On Fri, 2013-06-21 at 12:49 +1000, Alexey Kardashevskiy wrote:
>> On 06/21/2013 12:34 PM, Alex Williamson wrote:
>>
>>
>> Do not follow you, sorry. For x86, is it that MSI routing table which is
>> updated via KVM_SET_GSI_ROUTING in KVM? When there is no KVM, what piece of
>> code responds on msi_notify() in qemu-x86 and does qemu_irq_pulse()?
>
> vfio_msi_interrupt->msi[x]_notify->stl_le_phys(msg.address, msg.data)
>
> This writes directly to the interrupt block on the vCPU.  With KVM, the
> in-kernel APIC does the same write, where the pin to MSIMessage is setup
> by kvm_irqchip_add_msi_route and the pin is pulled by an irqfd.

What is this "interrupt block on the vCPU" you speak of?  I reviewed
the SDM and see nothing in the APIC protocol or the brief description
of MSI as a PCI concept that would indicate anything except that the
PHB handles MSI writes and feeds them to the I/O APIC.

In fact, the wikipedia article on MSI has:

"A common misconception with Message Signaled Interrupts is that they
allow the device to send data to a processor as part of the interrupt.
The data that is sent as part of the write is used by the chipset to
determine which interrupt to trigger on which processor; it is not
available for the device to communicate additional information to the
interrupt handler."

> Do I understand that on POWER the MSI from the device is intercepted at
> the PHB and converted to an IRQ that's triggered by some means other
> than a MSI write?

This is exactly the same thing that happens on x86, no?  Can you point
me to something in the SDM that says otherwise?

Regards,

Anthony Liguori

>  So to correctly model the hardware, vfio should do a
> msi_notify() that does a stl_le_phys that terminates at this IRQ
> remapper thing and in turn toggles a qemu_irq.  MSIMessage is only
> extraneous data if you want to skip over hardware blocks.
>
> Maybe you could add a device parameter to kvm_irqchip_add_msi_route so
> that it can be implemented on POWER without this pci_bus_map_msi
> interface that seems very unique to POWER.  Thanks,
>
> Alex
>
>> >>>> ---
>> >>>>  hw/misc/vfio.c           |   11 +++++++++--
>> >>>>  hw/pci/pci.c             |   13 +++++++++++++
>> >>>>  hw/ppc/spapr_pci.c       |   13 +++++++++++++
>> >>>>  hw/virtio/virtio-pci.c   |   26 ++++++++++++++++++++------
>> >>>>  include/hw/pci/pci.h     |    4 ++++
>> >>>>  include/hw/pci/pci_bus.h |    1 +
>> >>>>  6 files changed, 60 insertions(+), 8 deletions(-)
>> >>>>
>> >>>> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
>> >>>> index 14aac04..2d9eef7 100644
>> >>>> --- a/hw/misc/vfio.c
>> >>>> +++ b/hw/misc/vfio.c
>> >>>> @@ -639,7 +639,11 @@ 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 ? pci_bus_map_msi(vdev->pdev.bus, *msg) : -1;
>> >>>> +    if (vector->virq < 0) {
>> >>>> +        vector->virq = msg ? kvm_irqchip_add_msi_route(kvm_state, 
>> >>>> *msg) : -1;
>> >>>> +    }
>> >>>>      if (vector->virq < 0 ||
>> >>>>          kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
>> >>>>                                         vector->virq) < 0) {
>> >>>> @@ -807,7 +811,10 @@ 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 = pci_bus_map_msi(vdev->pdev.bus, msg);
>> >>>> +        if (vector->virq < 0) {
>> >>>> +            vector->virq = kvm_irqchip_add_msi_route(kvm_state, msg);
>> >>>> +        }
>> >>>>          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 a976e46..a9875e9 100644
>> >>>> --- a/hw/pci/pci.c
>> >>>> +++ b/hw/pci/pci.c
>> >>>> @@ -1254,6 +1254,19 @@ 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;
>> >>>> +}
>> >>>> +
>> >>>> +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 80408c9..9ef9a29 100644
>> >>>> --- a/hw/ppc/spapr_pci.c
>> >>>> +++ b/hw/ppc/spapr_pci.c
>> >>>> @@ -500,6 +500,18 @@ 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)
>> >>>> +{
>> >>>> +    DeviceState *par = bus->qbus.parent;
>> >>>> +    sPAPRPHBState *sphb = (sPAPRPHBState *) par;
>> >>>> +    unsigned long addr = msg.address - sphb->msi_win_addr;
>> >>>> +    int ndev = addr >> 16;
>> >>>> +    int vec = ((addr & 0xFFFF) >> 2) | msg.data;
>> >>>> +    uint32_t irq = sphb->msi_table[ndev].irq + vec;
>> >>>> +
>> >>>> +    return (int)irq;
>> >>>> +}
>> >>>> +
>> >>>>  static const MemoryRegionOps spapr_msi_ops = {
>> >>>>      /* There is no .read as the read result is undefined by PCI spec */
>> >>>>      .read = NULL,
>> >>>> @@ -664,6 +676,7 @@ 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 d309416..587f53e 100644
>> >>>> --- a/hw/virtio/virtio-pci.c
>> >>>> +++ b/hw/virtio/virtio-pci.c
>> >>>> @@ -472,6 +472,8 @@ static unsigned virtio_pci_get_features(DeviceState 
>> >>>> *d)
>> >>>>      return proxy->host_features;
>> >>>>  }
>> >>>>
>> >>>> +extern int spapr_msi_get_irq(PCIBus *bus, MSIMessage *msg);
>> >>>> +
>> >>>>  static int kvm_virtio_pci_vq_vector_use(VirtIOPCIProxy *proxy,
>> >>>>                                          unsigned int queue_no,
>> >>>>                                          unsigned int vector,
>> >>>> @@ -481,7 +483,10 @@ 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 = pci_bus_map_msi(proxy->pci_dev.bus, msg);
>> >>>> +        if (ret < 0) {
>> >>>> +            ret = kvm_irqchip_add_msi_route(kvm_state, msg);
>> >>>> +        }
>> >>>>          if (ret < 0) {
>> >>>>              return ret;
>> >>>>          }
>> >>>> @@ -609,14 +614,23 @@ static int 
>> >>>> virtio_pci_vq_vector_unmask(VirtIOPCIProxy *proxy,
>> >>>>      VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no);
>> >>>>      EventNotifier *n = virtio_queue_get_guest_notifier(vq);
>> >>>>      VirtIOIRQFD *irqfd;
>> >>>> -    int ret = 0;
>> >>>> +    int ret = 0, tmp;
>> >>>>
>> >>>>      if (proxy->vector_irqfd) {
>> >>>>          irqfd = &proxy->vector_irqfd[vector];
>> >>>> -        if (irqfd->msg.data != msg.data || irqfd->msg.address != 
>> >>>> msg.address) {
>> >>>> -            ret = kvm_irqchip_update_msi_route(kvm_state, irqfd->virq, 
>> >>>> msg);
>> >>>> -            if (ret < 0) {
>> >>>> -                return ret;
>> >>>> +
>> >>>> +        tmp = pci_bus_map_msi(proxy->pci_dev.bus, msg);
>> >>>> +        if (tmp >= 0) {
>> >>>> +            if (irqfd->virq != tmp) {
>> >>>> +                fprintf(stderr, "FIXME: MSI(-X) vector has changed 
>> >>>> from %X to %x\n",
>> >>>> +                        irqfd->virq, tmp);
>> >>>> +            }
>> >>>> +        } else {
>> >>>> +            if (irqfd->msg.data != msg.data || irqfd->msg.address != 
>> >>>> msg.address) {
>> >>>> +                ret = kvm_irqchip_update_msi_route(kvm_state, 
>> >>>> irqfd->virq, msg);
>> >>>> +                if (ret < 0) {
>> >>>> +                    return ret;
>> >>>> +                }
>> >>>>              }
>> >>>>          }
>> >>>>      }
>> >>>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
>> >>>> index 8797802..632739a 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;
>> >>>
>> >>>
>> >>>
>> >>
>> >>
>> >
>> >
>> >
>>
>>
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