Re: [Qemu-devel] [PATCH v4 08/10] vfio: vote the function 0 to do host bus reset when aer occurred

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

On Mon, 21 Mar 2016 18:08:44 +0800
Cao jin <caoj.fnst@cn.fujitsu.com> wrote:

> From: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> 
> Due to all devices assigned to VM on the same way as host if enable
> aer, so we can easily do the hot reset by selecting the function #0
> to do the hot reset.
> 
> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> ---
>  hw/vfio/pci.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/vfio/pci.h |  2 ++
>  2 files changed, 52 insertions(+)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 9902c87..718cde7 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -1900,6 +1900,8 @@ static void vfio_check_hot_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;
> @@ -2608,11 +2610,36 @@ static void vfio_put_device(VFIOPCIDevice *vdev)
>  static void vfio_err_notifier_handler(void *opaque)
>  {
>      VFIOPCIDevice *vdev = opaque;
> +    PCIDevice *pdev = &vdev->pdev;
>  
>      if (!event_notifier_test_and_clear(&vdev->err_notifier)) {
>          return;
>      }
>  
> +    if (vdev->features & VFIO_FEATURE_ENABLE_AER) {
> +        VFIOPCIDevice *tmp;
> +        PCIDevice *dev;
> +        int devfn;
> +
> +        /*
> +         * If one device has aer capability on a bus, when aer occurred,
> +         * we should notify all devices on the bus there was an aer arrived,
> +         * then we are able to vote the device #0 to do host bus reset.
> +         */
> +        for (devfn = 0; devfn < 8; devfn++) {

ARI?

> +            dev = pci_find_device(pdev->bus, pci_bus_num(pdev->bus),
> +                      PCI_DEVFN(PCI_SLOT(pdev->devfn), devfn));
> +            if (!dev) {
> +                continue;
> +            }
> +            if (!object_dynamic_cast(OBJECT(dev), "vfio-pci")) {
> +                continue;
> +            }
> +            tmp = DO_UPCAST(VFIOPCIDevice, pdev, dev);
> +            tmp->aer_occurred = true;
> +        }
> +    }
> +
>      /*
>       * TBD. Retrieve the error details and decide what action
>       * needs to be taken. One of the actions could be to pass
> @@ -3075,6 +3102,29 @@ static void vfio_pci_reset(DeviceState *dev)
>  
>      trace_vfio_pci_reset(vdev->vbasedev.name);
>  
> +    if (vdev->aer_occurred) {
> +        PCIDevice *br = pci_bridge_get_device(pdev->bus);
> +
> +        if (br &&
> +            (pci_get_word(br->config + PCI_BRIDGE_CONTROL) &
> +             PCI_BRIDGE_CTL_BUS_RESET)) {
> +            /* simply voting the function 0 to do hot bus reset */
> +            if (pci_get_function_0(pdev) == pdev) {
> +                if (vdev->features & VFIO_FEATURE_ENABLE_AER) {
> +                    vfio_pci_hot_reset(vdev, vdev->single_depend_dev);
> +                } else {
> +                    /* if this device has not AER capability, code
> +                     * coming here indicates there is another function
> +                     * on the bus has AER capability.
> +                     * */

This shouldn't be possible, right?

> +                    vfio_pci_hot_reset(vdev, false);
> +                }
> +            }
> +            vdev->aer_occurred = false;
> +            return;
> +        }
> +    }

Why do we care than an AER occurred now?  Can't we simply test:

    if (vdev->features & VFIO_FEATURE_ENABLE_AER &&
        pci_get_function_0(pdev) == pdev) {
        PCIDevice *br = pci_bridge_get_device(pdev->bus);

        if (pci_get_word(br->config + PCI_BRIDGE_CONTROL) &
            PCI_BRIDGE_CTL_BUS_RESET)) {

            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 db7c6d5..17c75b8 100644
> --- a/hw/vfio/pci.h
> +++ b/hw/vfio/pci.h
> @@ -143,6 +143,8 @@ typedef struct VFIOPCIDevice {
>      bool no_kvm_intx;
>      bool no_kvm_msi;
>      bool no_kvm_msix;
> +    bool aer_occurred;
> +    bool single_depend_dev;
>  } VFIOPCIDevice;
>  
>  uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len);