Re: [PATCH] vfio: Implement a common device info helper

[Robin Voetter <robin@streamhpc.com>]

On 6/1/23 16:45, Alex Williamson wrote:
> A common helper implementing the realloc algorithm for handling
> capabilities.
> 
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Reviewed-by: Cédric Le Goater <clg@redhat.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Robin Voetter <robin@streamhpc.com>

> ---
> 
> RFCv2 -> v1: Remove spurious semicolon
> 
>  hw/s390x/s390-pci-vfio.c      | 37 ++++------------------------
>  hw/vfio/common.c              | 46 ++++++++++++++++++++++++++---------
>  include/hw/vfio/vfio-common.h |  1 +
>  3 files changed, 41 insertions(+), 43 deletions(-)
> 
> diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
> index f51190d4662f..59a2e03873bd 100644
> --- a/hw/s390x/s390-pci-vfio.c
> +++ b/hw/s390x/s390-pci-vfio.c
> @@ -289,38 +289,11 @@ static void s390_pci_read_pfip(S390PCIBusDevice *pbdev,
>      memcpy(pbdev->zpci_fn.pfip, cap->pfip, CLP_PFIP_NR_SEGMENTS);
>  }
>  
> -static struct vfio_device_info *get_device_info(S390PCIBusDevice *pbdev,
> -                                                uint32_t argsz)
> +static struct vfio_device_info *get_device_info(S390PCIBusDevice *pbdev)
>  {
> -    struct vfio_device_info *info = g_malloc0(argsz);
> -    VFIOPCIDevice *vfio_pci;
> -    int fd;
> +    VFIOPCIDevice *vfio_pci = container_of(pbdev->pdev, VFIOPCIDevice, pdev);
>  
> -    vfio_pci = container_of(pbdev->pdev, VFIOPCIDevice, pdev);
> -    fd = vfio_pci->vbasedev.fd;
> -
> -    /*
> -     * If the specified argsz is not large enough to contain all capabilities
> -     * it will be updated upon return from the ioctl.  Retry until we have
> -     * a big enough buffer to hold the entire capability chain.  On error,
> -     * just exit and rely on CLP defaults.
> -     */
> -retry:
> -    info->argsz = argsz;
> -
> -    if (ioctl(fd, VFIO_DEVICE_GET_INFO, info)) {
> -        trace_s390_pci_clp_dev_info(vfio_pci->vbasedev.name);
> -        g_free(info);
> -        return NULL;
> -    }
> -
> -    if (info->argsz > argsz) {
> -        argsz = info->argsz;
> -        info = g_realloc(info, argsz);
> -        goto retry;
> -    }
> -
> -    return info;
> +    return vfio_get_device_info(vfio_pci->vbasedev.fd);
>  }
>  
>  /*
> @@ -335,7 +308,7 @@ bool s390_pci_get_host_fh(S390PCIBusDevice *pbdev, uint32_t *fh)
>  
>      assert(fh);
>  
> -    info = get_device_info(pbdev, sizeof(*info));
> +    info = get_device_info(pbdev);
>      if (!info) {
>          return false;
>      }
> @@ -356,7 +329,7 @@ void s390_pci_get_clp_info(S390PCIBusDevice *pbdev)
>  {
>      g_autofree struct vfio_device_info *info = NULL;
>  
> -    info = get_device_info(pbdev, sizeof(*info));
> +    info = get_device_info(pbdev);
>      if (!info) {
>          return;
>      }
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 78358ede2764..ed142296e9fe 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -2843,11 +2843,35 @@ void vfio_put_group(VFIOGroup *group)
>      }
>  }
>  
> +struct vfio_device_info *vfio_get_device_info(int fd)
> +{
> +    struct vfio_device_info *info;
> +    uint32_t argsz = sizeof(*info);
> +
> +    info = g_malloc0(argsz);
> +
> +retry:
> +    info->argsz = argsz;
> +
> +    if (ioctl(fd, VFIO_DEVICE_GET_INFO, info)) {
> +        g_free(info);
> +        return NULL;
> +    }
> +
> +    if (info->argsz > argsz) {
> +        argsz = info->argsz;
> +        info = g_realloc(info, argsz);
> +        goto retry;
> +    }
> +
> +    return info;
> +}
> +
>  int vfio_get_device(VFIOGroup *group, const char *name,
>                      VFIODevice *vbasedev, Error **errp)
>  {
> -    struct vfio_device_info dev_info = { .argsz = sizeof(dev_info) };
> -    int ret, fd;
> +    g_autofree struct vfio_device_info *info = NULL;
> +    int fd;
>  
>      fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
>      if (fd < 0) {
> @@ -2859,11 +2883,11 @@ int vfio_get_device(VFIOGroup *group, const char *name,
>          return fd;
>      }
>  
> -    ret = ioctl(fd, VFIO_DEVICE_GET_INFO, &dev_info);
> -    if (ret) {
> +    info = vfio_get_device_info(fd);
> +    if (!info) {
>          error_setg_errno(errp, errno, "error getting device info");
>          close(fd);
> -        return ret;
> +        return -1;
>      }
>  
>      /*
> @@ -2891,14 +2915,14 @@ int vfio_get_device(VFIOGroup *group, const char *name,
>      vbasedev->group = group;
>      QLIST_INSERT_HEAD(&group->device_list, vbasedev, next);
>  
> -    vbasedev->num_irqs = dev_info.num_irqs;
> -    vbasedev->num_regions = dev_info.num_regions;
> -    vbasedev->flags = dev_info.flags;
> +    vbasedev->num_irqs = info->num_irqs;
> +    vbasedev->num_regions = info->num_regions;
> +    vbasedev->flags = info->flags;
> +
> +    trace_vfio_get_device(name, info->flags, info->num_regions, info->num_irqs);
>  
> -    trace_vfio_get_device(name, dev_info.flags, dev_info.num_regions,
> -                          dev_info.num_irqs);
> +    vbasedev->reset_works = !!(info->flags & VFIO_DEVICE_FLAGS_RESET);
>  
> -    vbasedev->reset_works = !!(dev_info.flags & VFIO_DEVICE_FLAGS_RESET);
>      return 0;
>  }
>  
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index eed244f25f34..a8dcda592c08 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -212,6 +212,7 @@ void vfio_region_finalize(VFIORegion *region);
>  void vfio_reset_handler(void *opaque);
>  VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp);
>  void vfio_put_group(VFIOGroup *group);
> +struct vfio_device_info *vfio_get_device_info(int fd);
>  int vfio_get_device(VFIOGroup *group, const char *name,
>                      VFIODevice *vbasedev, Error **errp);
>