Re: [Qemu-devel] [PATCH v2 09/11] vfio: vote a device to do host bus reset

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 9 Mar 2016 18:39:51 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Mon, Mar 07, 2016 at 11:23:02AM +0800, Cao jin wrote:
> > From: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> > 
> > Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> > ---
> >  hw/vfio/pci.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  hw/vfio/pci.h |  1 +
> >  2 files changed, 58 insertions(+)
> > 
> > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> > index 24848c9..8e902d2 100644
> > --- a/hw/vfio/pci.c
> > +++ b/hw/vfio/pci.c
> > @@ -1937,6 +1937,8 @@ static void vfio_check_host_bus_reset(VFIOPCIDevice *vdev, Error **errp)
> >      /* List all affected devices by bus reset */
> >      devices = &info->devices[0];
> >  
> > +    vdev->single_depend_dev = (info->count == 1);
> > +
> >      /* Verify that we have all the groups required */
> >      for (i = 0; i < info->count; i++) {
> >          PCIHostDeviceAddress host;
> > @@ -2998,6 +3000,49 @@ static void vfio_exitfn(PCIDevice *pdev)
> >      vfio_unregister_bars(vdev);
> >  }
> >  
> > +static VFIOPCIDevice *vfio_pci_get_do_reset_device(VFIOPCIDevice *vdev)
> > +{
> > +    struct vfio_pci_hot_reset_info *info = NULL;
> > +    struct vfio_pci_dependent_device *devices;
> > +    VFIOGroup *group;
> > +    VFIODevice *vbasedev_iter;
> > +    int ret;
> > +
> > +    ret = vfio_get_hot_reset_info(vdev, &info);
> > +    if (ret) {
> > +        error_report("vfio: Cannot enable AER for device %s,"
> > +                     " device does not support hot reset.",
> > +                     vdev->vbasedev.name);
> > +        return NULL;
> > +    }
> > +
> > +    devices = &info->devices[0];
> > +
> > +    QLIST_FOREACH(group, &vfio_group_list, next) {
> > +        if (group->groupid == devices[0].group_id) {
> > +            break;
> > +        }
> > +    }
> > +
> > +    if (!group) {
> > +        error_report("vfio: Cannot enable AER for device %s, "
> > +                    "depends on group %d which is not owned.",
> > +                    vdev->vbasedev.name, devices[0].group_id);
> > +        return NULL;
> > +    }
> > +
> > +    QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
> > +        if (vbasedev_iter->type != VFIO_DEVICE_TYPE_PCI ||
> > +            !(vdev->features & VFIO_FEATURE_ENABLE_AER)) {
> > +            continue;
> > +        }
> > +
> > +        return container_of(vbasedev_iter, VFIOPCIDevice, vbasedev);
> > +    }
> > +
> > +    return NULL;
> > +}
> > +
> >  static void vfio_pci_reset(DeviceState *dev)
> >  {
> >      PCIDevice *pdev = DO_UPCAST(PCIDevice, qdev, dev);
> > @@ -3005,6 +3050,18 @@ static void vfio_pci_reset(DeviceState *dev)
> >  
> >      trace_vfio_pci_reset(vdev->vbasedev.name);
> >  
> > +    if (pdev->bus->in_hot_reset) {  
> 
> After discussing this with Alex, I think what you
> really are looking for is
>      if (dev->realized)
> in order to skip hot reset when device is plugged-in
> initially.

Seems fragile, device_reset() also gets called via pci_device_reset()
which would happen if we hooked up FLR to the device.  That's clearly
intended to be a function local reset, as is I believe the dc->reset
itself, so assuming behavior based on states like dev->realized is
likely to break.  Either we need some external hints, like what's added
here, or we need a separate callback for a bus reset.  Thanks,

Alex

> > +        VFIOPCIDevice *tmp;
> > +
> > +        tmp = vfio_pci_get_do_reset_device(vdev);
> > +        if (tmp) {
> > +            if (tmp == vdev) {
> > +                vfio_pci_hot_reset(vdev, vdev->single_depend_dev);
> > +            }
> > +            return;
> > +        }
> > +    }
> > +
> >      vfio_pci_pre_reset(vdev);
> >  
> >      if (vdev->resetfn && !vdev->resetfn(vdev)) {
> > diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
> > index aff46c2..32bd31f 100644
> > --- a/hw/vfio/pci.h
> > +++ b/hw/vfio/pci.h
> > @@ -143,6 +143,7 @@ typedef struct VFIOPCIDevice {
> >      bool no_kvm_intx;
> >      bool no_kvm_msi;
> >      bool no_kvm_msix;
> > +    bool single_depend_dev;
> >  } VFIOPCIDevice;
> >  
> >  uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len);
> > -- 
> > 1.9.3
> > 
> >