Re: [dpdk-dev] [PATCH 2/2] net/virtio: do not require IO permissions

[Tiwei Bie <tiwei.bie@intel.com>]

On Thu, Oct 17, 2019 at 01:56:28PM +0200, David Marchand wrote:
> On x86, iopl permissions are only needed when the virtio devices are
> bound to a uio kernel module.
> 
> When running a dpdk application as non root, the virtio driver was
> refusing to register because of this check while it could work when
> binding the device to vfio (requires to have a vIOMMU configured).
> 
> We still need to call rte_eal_iopl_init() in the constructor so that
> the interrupt thread would inherit this permission in the case it could
> be used with UIO later.
> Log a warning message for the user to understand what is wrong.
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>  drivers/net/virtio/virtio_ethdev.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index 7261109..3506ca0 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -1995,11 +1995,6 @@ exit:
>  static int eth_virtio_pci_probe(struct rte_pci_driver *pci_drv __rte_unused,
>  	struct rte_pci_device *pci_dev)
>  {
> -	if (rte_eal_iopl_init() != 0) {
> -		PMD_INIT_LOG(ERR, "IOPL call failed - cannot use virtio PMD");
> -		return 1;
> -	}
> -
>  	/* virtio pmd skips probe if device needs to work in vdpa mode */
>  	if (vdpa_mode_selected(pci_dev->device.devargs))
>  		return 1;
> @@ -2031,7 +2026,8 @@ static struct rte_pci_driver rte_virtio_pmd = {
>  
>  RTE_INIT(rte_virtio_pmd_init)
>  {
> -	rte_eal_iopl_init();
> +	if (rte_eal_iopl_init() != 0)
> +		PMD_INIT_LOG(WARNING, "IOPL call failed - virtio devices won't be functional if bound to UIO drivers");

Basically this will undo what below commit did, i.e.
annoying log will show again.

https://github.com/DPDK/dpdk/commit/705dced4a72a1053368c84c4b68f04f028a78b30

Maybe it's better to print this error when we really
need the port IO (legacy device):

https://github.com/DPDK/dpdk/blob/31b798a6f08e9b333b94b8bb26910209aa810b73/drivers/net/virtio/virtio_pci.c#L679-L680
https://github.com/DPDK/dpdk/blob/31b798a6f08e9b333b94b8bb26910209aa810b73/drivers/net/virtio/virtio_ethdev.c#L1834-L1835

Thanks,
Tiwei

>  	rte_pci_register(&rte_virtio_pmd);
>  }
>  
> -- 
> 1.8.3.1
>