Re: [Qemu-devel] [PATCH 1/2] kvm irqfd: support msimessage to irq translation in PHB

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 19, 2013 at 05:44:04PM +1000, Alexey Kardashevskiy wrote:
> On 08/19/2013 05:35 PM, Michael S. Tsirkin wrote:
> > On Wed, Aug 07, 2013 at 06:51:32PM +1000, Alexey Kardashevskiy 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 tries a bus specific map_msi and falls back to
> >> the default kvm_irqchip_add_msi_route() if none set.
> >>
> >> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > 
> > The mapping (irq # within data) is really KVM on PPC64 specific,
> > isn't it?
> > 
> > So why not implement
> > kvm_irqchip_add_msi_route(kvm_state, msg);
> > to simply return msg.data on PPC64?
> 
> How exactly? Please give some details. kvm_irqchip_add_msi_route() is
> implemented in kvm-all.c once for all platforms so hack it right there?

You can add the map_msi callback in kvm state,
then just call it if it's set, right?

> I thought we discussed all of this already and decided that this thing
> should go to PCI host bridge and by default PHB's map_msi() callback should
> just call kvm_irqchip_add_msi_route(). This is why I touched i386.
> 
> Things have changed since then?


I think pci_bus_map_msi was there since day 1, it's not like
we are going back and forth on it, right?

I always felt it's best to have irqfd isolated to kvm somehow
rather than have hooks in pci code, I just don't know enough
about kvm on ppc to figure out the right way to do this.
With your latest patches I think this is becoming clearer ...

> 
> > Then you won't have to change all the rest of the code.
> > 
> >> ---
> >> Changes:
> >> 2013/08/07 v5:
> >> * pci_bus_map_msi now has default behaviour which is to call
> >> kvm_irqchip_add_msi_route
> >> * kvm_irqchip_release_virq fixed not crash when there is no routes
> >> ---
> >>  hw/i386/kvm/pci-assign.c | 4 ++--
> >>  hw/misc/vfio.c           | 4 ++--
> >>  hw/pci/pci.c             | 9 +++++++++
> >>  hw/virtio/virtio-pci.c   | 2 +-
> >>  include/hw/pci/pci.h     | 2 ++
> >>  include/hw/pci/pci_bus.h | 1 +
> >>  kvm-all.c                | 3 +++
> >>  7 files changed, 20 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/hw/i386/kvm/pci-assign.c b/hw/i386/kvm/pci-assign.c
> >> index 5618173..fb59982 100644
> >> --- a/hw/i386/kvm/pci-assign.c
> >> +++ b/hw/i386/kvm/pci-assign.c
> >> @@ -1008,9 +1008,9 @@ static void assigned_dev_update_msi(PCIDevice *pci_dev)
> >>          MSIMessage msg = msi_get_message(pci_dev, 0);
> >>          int virq;
> >>  
> >> -        virq = kvm_irqchip_add_msi_route(kvm_state, msg);
> >> +        virq = pci_bus_map_msi(kvm_state, pci_dev->bus, msg);
> >>          if (virq < 0) {
> >> -            perror("assigned_dev_update_msi: kvm_irqchip_add_msi_route");
> >> +            perror("assigned_dev_update_msi: pci_bus_map_msi");
> >>              return;
> >>          }
> >>
> > 
> > This really confuses me. Why are you changing i386 code?
> > 
> >   
> >> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
> >> index 017e693..adcd23d 100644
> >> --- a/hw/misc/vfio.c
> >> +++ b/hw/misc/vfio.c
> >> @@ -643,7 +643,7 @@ 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(kvm_state, vdev->pdev.bus, *msg) : -1;
> >>      if (vector->virq < 0 ||
> >>          kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
> >>                                         vector->virq) < 0) {
> >> @@ -811,7 +811,7 @@ 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(kvm_state, vdev->pdev.bus, 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 4c004f5..4bce3e7 100644
> >> --- a/hw/pci/pci.c
> >> +++ b/hw/pci/pci.c
> >> @@ -1249,6 +1249,15 @@ void pci_device_set_intx_routing_notifier(PCIDevice *dev,
> >>      dev->intx_routing_notifier = notifier;
> >>  }
> >>  
> >> +int pci_bus_map_msi(KVMState *s, PCIBus *bus, MSIMessage msg)
> >> +{
> >> +    if (bus->map_msi) {
> >> +        return bus->map_msi(s, bus, msg);
> >> +    }
> >> +
> >> +    return kvm_irqchip_add_msi_route(s, msg);
> >> +}
> >> +
> >>  /*
> >>   * PCI-to-PCI bridge specification
> >>   * 9.1: Interrupt routing. Table 9-1
> >> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> >> index d37037e..21180d2 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 = pci_bus_map_msi(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 ccec2ba..b6ad9e4 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)(KVMState *s, PCIBus *bus, MSIMessage msg);
> >>  
> >>  typedef enum {
> >>      PCI_HOTPLUG_DISABLED,
> >> @@ -375,6 +376,7 @@ 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);
> >> +int pci_bus_map_msi(KVMState *s, 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 9df1788..5bf7994 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/kvm-all.c b/kvm-all.c
> >> index 716860f..3ae5274 100644
> >> --- a/kvm-all.c
> >> +++ b/kvm-all.c
> >> @@ -1069,6 +1069,9 @@ void kvm_irqchip_release_virq(KVMState *s, int virq)
> >>      struct kvm_irq_routing_entry *e;
> >>      int i;
> >>  
> >> +    if (!s->irq_routes) {
> >> +        return;
> >> +    }
> >>      for (i = 0; i < s->irq_routes->nr; i++) {
> >>          e = &s->irq_routes->entries[i];
> >>          if (e->gsi == virq) {
> >> -- 
> >> 1.8.3.2
> 
> 
> -- 
> Alexey