Re: [PATCH 3/5] vfio/pci: Respond to KVM irqchip change notifier

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Nov 22, 2019 at 06:12:57AM +0100, Greg Kurz wrote:
> On Thu, 21 Nov 2019 11:56:05 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > VFIO PCI devices already respond to the pci intx routing notifier, in order
> > to update kernel irqchip mappings when routing is updated.  However this
> > won't handle the case where the irqchip itself is replaced by a different
> > model while retaining the same routing.  This case can happen on
> > the pseries machine type due to PAPR feature negotiation.
> > 
> > To handle that case, add a handler for the irqchip change notifier, which
> > does much the same thing as the routing notifier, but is unconditional,
> > rather than being a no-op when the routing hasn't changed.
> > 
> > Cc: Alex Williamson <alex.williamson@redhat.com>
> > Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/vfio/pci.c | 23 ++++++++++++++++++-----
> >  hw/vfio/pci.h |  1 +
> >  2 files changed, 19 insertions(+), 5 deletions(-)
> > 
> > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> > index 521289aa7d..95478c2c55 100644
> > --- a/hw/vfio/pci.c
> > +++ b/hw/vfio/pci.c
> > @@ -256,6 +256,14 @@ static void vfio_intx_routing_notifier(PCIDevice *pdev)
> >      }
> >  }
> >  
> > +static void vfio_irqchip_change(Notifier *notify, void *data)
> > +{
> > +    VFIOPCIDevice *vdev = container_of(notify, VFIOPCIDevice,
> > +                                       irqchip_change_notifier);
> > +
> > +    vfio_intx_update(vdev, &vdev->intx.route);
> > +}
> > +
> >  static int vfio_intx_enable(VFIOPCIDevice *vdev, Error **errp)
> >  {
> >      uint8_t pin = vfio_pci_read_config(&vdev->pdev, PCI_INTERRUPT_PIN, 1);
> > @@ -2973,16 +2981,18 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
> >                                                    vfio_intx_mmap_enable, vdev);
> >          pci_device_set_intx_routing_notifier(&vdev->pdev,
> >                                               vfio_intx_routing_notifier);
> > +        vdev->irqchip_change_notifier.notify = vfio_irqchip_change;
> > +        kvm_irqchip_add_change_notifier(&vdev->irqchip_change_notifier);
> >          ret = vfio_intx_enable(vdev, errp);
> >          if (ret) {
> > -            goto out_teardown;
> > +            goto out_deregister;
> >          }
> >      }
> >  
> >      if (vdev->display != ON_OFF_AUTO_OFF) {
> >          ret = vfio_display_probe(vdev, errp);
> >          if (ret) {
> > -            goto out_teardown;
> > +            goto out_deregister;
> >          }
> >      }
> >      if (vdev->enable_ramfb && vdev->dpy == NULL) {
> > @@ -2992,11 +3002,11 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
> >      if (vdev->display_xres || vdev->display_yres) {
> >          if (vdev->dpy == NULL) {
> >              error_setg(errp, "xres and yres properties require display=on");
> > -            goto out_teardown;
> > +            goto out_deregister;
> >          }
> >          if (vdev->dpy->edid_regs == NULL) {
> >              error_setg(errp, "xres and yres properties need edid support");
> > -            goto out_teardown;
> > +            goto out_deregister;
> >          }
> >      }
> >  
> 
> After this change, we end up with:
> 
>     if (vfio_pci_read_config(&vdev->pdev, PCI_INTERRUPT_PIN, 1)) {
>         vdev->intx.mmap_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
>                                                   vfio_intx_mmap_enable, vdev);
>         pci_device_set_intx_routing_notifier(&vdev->pdev,
>                                              vfio_intx_routing_notifier);
>         vdev->irqchip_change_notifier.notify = vfio_irqchip_change;
>         kvm_irqchip_add_change_notifier(&vdev->irqchip_change_notifier);
>         ret = vfio_intx_enable(vdev, errp);
>         if (ret) {
>             goto out_deregister;
>         }
>     }
> 
>     if (vdev->display != ON_OFF_AUTO_OFF) {
>         ret = vfio_display_probe(vdev, errp);
>         if (ret) {
>             goto out_deregister;
>         }
>     }
>     if (vdev->enable_ramfb && vdev->dpy == NULL) {
>         error_setg(errp, "ramfb=on requires display=on");
>         goto out_teardown;
>              ^^^^^^^^^^^^
> 
> This should be out_deregister.

Oops, fixed in my tree.

> The enable_ramfb property belongs to the nohotplug variant. It
> means QEMU is going to terminate and we probably don't really
> care to leak notifiers, but this still looks weird and fragile,
> if enable_ramfb ever becomes usable by hotpluggable devices
> one day.
> 
>     }
>     if (vdev->display_xres || vdev->display_yres) {
>         if (vdev->dpy == NULL) {
>             error_setg(errp, "xres and yres properties require display=on");
>             goto out_deregister;
>         }
>         if (vdev->dpy->edid_regs == NULL) {
>             error_setg(errp, "xres and yres properties need edid support");
>             goto out_deregister;
>         }
>     }
> 
> 
> > @@ -3020,8 +3030,10 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
> >  
> >      return;
> >  
> > -out_teardown:
> > +out_deregister:
> >      pci_device_set_intx_routing_notifier(&vdev->pdev, NULL);
> > +    kvm_irqchip_remove_change_notifier(&vdev->irqchip_change_notifier);
> > +out_teardown:
> >      vfio_teardown_msi(vdev);
> >      vfio_bars_exit(vdev);
> >  error:
> > @@ -3064,6 +3076,7 @@ static void vfio_exitfn(PCIDevice *pdev)
> >      vfio_unregister_req_notifier(vdev);
> >      vfio_unregister_err_notifier(vdev);
> >      pci_device_set_intx_routing_notifier(&vdev->pdev, NULL);
> > +    kvm_irqchip_remove_change_notifier(&vdev->irqchip_change_notifier);
> >      vfio_disable_interrupts(vdev);
> >      if (vdev->intx.mmap_timer) {
> >          timer_free(vdev->intx.mmap_timer);
> > diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
> > index b329d50338..35626cd63e 100644
> > --- a/hw/vfio/pci.h
> > +++ b/hw/vfio/pci.h
> > @@ -169,6 +169,7 @@ typedef struct VFIOPCIDevice {
> >      bool enable_ramfb;
> >      VFIODisplay *dpy;
> >      Error *migration_blocker;
> > +    Notifier irqchip_change_notifier;
> >  } VFIOPCIDevice;
> >  
> >  uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len);
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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