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

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

On Wed, Mar 09, 2016 at 10:09:11AM -0700, Alex Williamson wrote:
> 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.

You can check that as well (through config space, no need
for new flags).

There's also PM reset.

>  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


So I'm fine with a new flag is_bus_rst, or an API pci_is_bus_rst.

But it has to be set whenever bus is reset, *not* just on secondary bus reset.


> > > +        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
> > > 
> > >