Re: [PATCH v5 01/13] vfio/pci: Extract mdev check into an helper

[Eric Auger]

On 7/19/24 14:04, Joao Martins wrote:
> In preparation to skip initialization of the HostIOMMUDevice for mdev,
> extract the checks that validate if a device is an mdev into helpers.
>
> A vfio_device_is_mdev() is created, and subsystems consult VFIODevice::mdev
> to check if it's mdev or not.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  include/hw/vfio/vfio-common.h |  2 ++
>  hw/vfio/helpers.c             | 14 ++++++++++++++
>  hw/vfio/pci.c                 | 12 +++---------
>  3 files changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index e8ddf92bb185..98acae8c1c97 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -116,6 +116,7 @@ typedef struct VFIODevice {
>      DeviceState *dev;
>      int fd;
>      int type;
> +    bool mdev;
>      bool reset_works;
>      bool needs_reset;
>      bool no_mmap;
> @@ -231,6 +232,7 @@ void vfio_region_exit(VFIORegion *region);
>  void vfio_region_finalize(VFIORegion *region);
>  void vfio_reset_handler(void *opaque);
>  struct vfio_device_info *vfio_get_device_info(int fd);
> +bool vfio_device_is_mdev(VFIODevice *vbasedev);
>  bool vfio_attach_device(char *name, VFIODevice *vbasedev,
>                          AddressSpace *as, Error **errp);
>  void vfio_detach_device(VFIODevice *vbasedev);
> diff --git a/hw/vfio/helpers.c b/hw/vfio/helpers.c
> index b14edd46edc9..7e23e9080c9d 100644
> --- a/hw/vfio/helpers.c
> +++ b/hw/vfio/helpers.c
> @@ -675,3 +675,17 @@ int vfio_device_get_aw_bits(VFIODevice *vdev)
>  
>      return HOST_IOMMU_DEVICE_CAP_AW_BITS_MAX;
>  }
> +
> +bool vfio_device_is_mdev(VFIODevice *vbasedev)
> +{
> +    g_autofree char *subsys = NULL;
> +    g_autofree char *tmp = NULL;
> +
> +    if (!vbasedev->sysfsdev) {
> +        return false;
> +    }
> +
> +    tmp = g_strdup_printf("%s/subsystem", vbasedev->sysfsdev);
> +    subsys = realpath(tmp, NULL);
> +    return subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
> +}
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index e03d9f3ba546..b34e91468a53 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2963,12 +2963,9 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>      ERRP_GUARD();
>      VFIOPCIDevice *vdev = VFIO_PCI(pdev);
>      VFIODevice *vbasedev = &vdev->vbasedev;
> -    char *subsys;
>      int i, ret;
> -    bool is_mdev;
>      char uuid[UUID_STR_LEN];
>      g_autofree char *name = NULL;
> -    g_autofree char *tmp = NULL;
>  
>      if (vbasedev->fd < 0 && !vbasedev->sysfsdev) {
>          if (!(~vdev->host.domain || ~vdev->host.bus ||
> @@ -2997,14 +2994,11 @@ static void vfio_realize(PCIDevice *pdev, Error 
> **errp)
>       * stays in sync with the active working set of the guest driver.  
> Prevent
>       * the x-balloon-allowed option unless this is minimally an mdev device.
>       */
> -    tmp = g_strdup_printf("%s/subsystem", vbasedev->sysfsdev);
> -    subsys = realpath(tmp, NULL);
> -    is_mdev = subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
> -    free(subsys);
> +    vbasedev->mdev = vfio_device_is_mdev(vbasedev);
>  
> -    trace_vfio_mdev(vbasedev->name, is_mdev);
> +    trace_vfio_mdev(vbasedev->name, vbasedev->mdev);
>  
> -    if (vbasedev->ram_block_discard_allowed && !is_mdev) {
> +    if (vbasedev->ram_block_discard_allowed && !vbasedev->mdev) {
>          error_setg(errp, "x-balloon-allowed only potentially compatible "
>                     "with mdev devices");
>          goto error;