[RFC,v8.1,01/13] vfio: extract vfio_get_hot_reset_info as a single function

the function is used to get affected devices by bus reset.
so here extract it, and can used for aer soon.

Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
---
 hw/vfio/pci.c | 67 +++++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 49 insertions(+), 18 deletions(-)

On Wed, 2015-05-27 at 10:46 +0800, Chen Fan wrote:
> the function is used to get affected devices by bus reset.
> so here extract it, and can used for aer soon.
> 
> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> ---
>  hw/vfio/pci.c | 67 +++++++++++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 49 insertions(+), 18 deletions(-)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index e0e339a..9c05304 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2641,6 +2641,50 @@ static void vfio_check_af_flr(VFIOPCIDevice *vdev, uint8_t pos)
>      }
>  }
>  
> +/*
> + * return negative with errno, return 0 on success.
> + * if success, the point of ret_info fill with the affected device reset info.
> + *
> + */
> +static int vfio_get_hot_reset_info(VFIOPCIDevice *vdev,
> +                                   struct vfio_pci_hot_reset_info **ret_info)
> +{
> +    struct vfio_pci_hot_reset_info *info;
> +    int ret, count;
> +
> +    *ret_info = NULL;
> +
> +    info = g_malloc0(sizeof(*info));
> +    info->argsz = sizeof(*info);
> +
> +    ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_PCI_HOT_RESET_INFO, info);
> +    if (ret && errno != ENOSPC) {
> +        ret = -errno;
> +        goto error;
> +    }
> +
> +    count = info->count;
> +
> +    info = g_realloc(info, sizeof(*info) +
> +                     (count * sizeof(struct vfio_pci_dependent_device)));
> +    info->argsz = sizeof(*info) +
> +                  (count * sizeof(struct vfio_pci_dependent_device));
> +
> +    ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_PCI_HOT_RESET_INFO, info);
> +    if (ret) {
> +        ret = -errno;
> +        goto error;
> +    }
> +
> +    *ret_info = info;
> +    info = NULL;
> +
> +    ret = 0;

Just return 0 here.

> +error:
> +    g_free(info);
> +    return ret;
> +}
> +
>  static int vfio_add_std_cap(VFIOPCIDevice *vdev, uint8_t pos)
>  {
>      PCIDevice *pdev = &vdev->pdev;
> @@ -2780,7 +2824,7 @@ static bool vfio_pci_host_match(PCIHostDeviceAddress *host1,
>  static int vfio_pci_hot_reset(VFIOPCIDevice *vdev, bool single)
>  {
>      VFIOGroup *group;
> -    struct vfio_pci_hot_reset_info *info;
> +    struct vfio_pci_hot_reset_info *info = NULL;
>      struct vfio_pci_dependent_device *devices;
>      struct vfio_pci_hot_reset *reset;
>      int32_t *fds;
> @@ -2792,32 +2836,19 @@ static int vfio_pci_hot_reset(VFIOPCIDevice *vdev, bool single)
>      vfio_pci_pre_reset(vdev);
>      vdev->vbasedev.needs_reset = false;
>  
> -    info = g_malloc0(sizeof(*info));
> -    info->argsz = sizeof(*info);
> -
> -    ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_PCI_HOT_RESET_INFO, info);
> -    if (ret && errno != ENOSPC) {
> -        ret = -errno;
> +    ret = vfio_get_hot_reset_info(vdev, &info);
> +    if (ret) {
>          if (!vdev->has_pm_reset) {
>              error_report("vfio: Cannot reset device %04x:%02x:%02x.%x, "
>                           "no available reset mechanism.", vdev->host.domain,
>                           vdev->host.bus, vdev->host.slot, vdev->host.function);
> +        } else {
> +            error_report("vfio: hot reset info failed: %m");

What if we pass through a root complex device where we can't do a bus
reset.  With this change, we get this useless error_report every time we
come through this path.  There are cases where this is not an error and
should not be reported to the user.

>          }
>          goto out_single;
>      }
>  
> -    count = info->count;
> -    info = g_realloc(info, sizeof(*info) + (count * sizeof(*devices)));
> -    info->argsz = sizeof(*info) + (count * sizeof(*devices));
>      devices = &info->devices[0];
> -
> -    ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_PCI_HOT_RESET_INFO, info);
> -    if (ret) {
> -        ret = -errno;
> -        error_report("vfio: hot reset info failed: %m");
> -        goto out_single;
> -    }
> -
>      trace_vfio_pci_hot_reset_has_dep_devices(vdev->vbasedev.name);
>  
>      /* Verify that we have all the groups required */