Re: [PATCH v4 01/12] vfio/pci: Extract mdev check into an helper

["Cédric Le Goater" <clg@redhat.com>]

Hello Joao

On 7/12/24 13:46, 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_set_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>
> ---
>   include/hw/vfio/vfio-common.h |  2 ++
>   hw/vfio/helpers.c             | 18 ++++++++++++++++++
>   hw/vfio/pci.c                 |  9 ++-------
>   3 files changed, 22 insertions(+), 7 deletions(-)
> 
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index e8ddf92bb185..7419466bca92 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);
> +void vfio_set_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..bace0e788a09 100644
> --- a/hw/vfio/helpers.c
> +++ b/hw/vfio/helpers.c
> @@ -675,3 +675,21 @@ int vfio_device_get_aw_bits(VFIODevice *vdev)
>   
>       return HOST_IOMMU_DEVICE_CAP_AW_BITS_MAX;
>   }
> +
> +void vfio_set_mdev(VFIODevice *vbasedev)

Could you please change this routine to :

   bool vfio_device_is_mdev(VFIODevice *vbasedev)

> +{
> +    g_autofree char *tmp = NULL;
> +    char *subsys;

a g_autofree variable is preferable here.

> +    bool is_mdev;
> +
> +    if (!vbasedev->sysfsdev) {
> +        return;
> +    }
> +
> +    tmp = g_strdup_printf("%s/subsystem", vbasedev->sysfsdev);
> +    subsys = realpath(tmp, NULL);
> +    is_mdev = subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);

simply return is the result here and ....

> +    free(subsys);
> +
> +    vbasedev->mdev = is_mdev;
> +}
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index e03d9f3ba546..585f23a18406 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2963,12 +2963,10 @@ 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 ||
> @@ -2997,11 +2995,8 @@ 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);
> -
> +    vfio_set_mdev(vbasedev);
> +    is_mdev = vbasedev->mdev;

replace with :

   vbasedev->mdev = vfio_device_is_mdev(vbasedev);

and use vbasedev->mdev instead of is_mdev where needed.


Thanks,

C.




>       trace_vfio_mdev(vbasedev->name, is_mdev);
>   
>       if (vbasedev->ram_block_discard_allowed && !is_mdev) {