Re: [Qemu-devel] [PATCH 08/10] vfio: introduce last reset sequence id

[Michael S. Tsirkin]

On Wed, Feb 17, 2016 at 06:43:52PM +0800, Cao jin wrote:
> From: Chen Fan <address@hidden>
> 
> avoid multi-reset host bus, we introduce sequence id to specify which
> bus is resetting. and if one of the dependent devices has done a reset.
> the others should skip.
> 
> Signed-off-by: Chen Fan <address@hidden>


I don't see why it's needed. All devices on same bus always
undergo bus reset together. Just select a representative (e.g.
smallest devfn) and reset from that.

> ---
>  hw/vfio/pci.c | 14 ++++++++++++++
>  hw/vfio/pci.h |  3 +++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index b900f70..5b885e7 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -1951,6 +1951,8 @@ static int vfio_check_host_bus_reset(VFIOPCIDevice 
> *vdev)
>      /* 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;
> @@ -2283,6 +2285,7 @@ static int vfio_pci_hot_reset(VFIOPCIDevice *vdev, bool 
> single)
>  
>      vfio_pci_pre_reset(vdev);
>      vdev->vbasedev.needs_reset = false;
> +    vdev->last_bus_reset_seqid = vdev->pdev.bus->reset_seqid;
>  
>      ret = vfio_get_hot_reset_info(vdev, &info);
>      if (ret) {
> @@ -2344,6 +2347,7 @@ static int vfio_pci_hot_reset(VFIOPCIDevice *vdev, bool 
> single)
>                  }
>                  vfio_pci_pre_reset(tmp);
>                  tmp->vbasedev.needs_reset = false;
> +                tmp->last_bus_reset_seqid = vdev->pdev.bus->reset_seqid;
>                  multi = true;
>                  break;
>              }
> @@ -3040,6 +3044,16 @@ static void vfio_pci_reset(DeviceState *dev)
>  
>      trace_vfio_pci_reset(vdev->vbasedev.name);
>  
> +    /* if need to do a hot reset */
> +    if (pdev->bus->bus_in_reset) {
> +        if (vdev->last_bus_reset_seqid == pdev->bus->reset_seqid) {
> +            return;
> +        } else if ((vdev->features & VFIO_FEATURE_ENABLE_AER)) {
> +            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 bf9e93c..684931d 100644
> --- a/hw/vfio/pci.h
> +++ b/hw/vfio/pci.h
> @@ -144,6 +144,9 @@ typedef struct VFIOPCIDevice {
>      bool no_kvm_msi;
>      bool no_kvm_msix;
>  
> +    bool single_depend_dev;
> +    uint32_t last_bus_reset_seqid;
> +
>      NotifierWithReturn hotplug_notifier;
>  } VFIOPCIDevice;
>  
> -- 
> 1.9.3
> 
>