Re: [PATCH] net/virtio-user: fix multi-process issue

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Thu, Feb 23, 2017 at 01:58:16PM +0200, Ami Sabo wrote:
> Secondary process doesn't properly attach to the rte_eth_device
> initialized by the primary process.
> 
> Accessing device from secondary process (e.g. via rte_eth_rx_burst),
> causes process to crash. because rte_eth_dev_data is not properly set.
> 
> The issue was flood by
> 'commit 7f95f78a8aea ("ethdev: clear data when allocating device")'
> which now clears rte_eth_dev_data entry.
> 
> So, most of the rte_eth_dev_data fields are not initialized.
> For pci devices these fields are initialized  by rte_eth_dev_pci_probe
> ->eth_dev_attach_secondary().
> However, for virtio-user virtio_user_pmd_probe() is called instead of
> rte_eth_dev_pci_probe().
> To fix it:  Allow non-pci drivers call to dev_attach_secondary() and
> call it (for secondary process) from virtio_user_pmd_probe.
> 
> Signed-off-by: Ami Sabo <amis@radware.com>

Firstly, two minor comments:

- A fix path needs a fixline (check dpdk.org/dev for HOWTO)

- It fixes a bug in former releases, thus it need be picked into a stable
  release. Then you need add following just before you Signed-off-by:

     Cc: stable@dpdk.org

>  /**
>   * @internal
> + * Attach to the ethdev already initialized by the primary
> + * process.
> + *
> + * @param	name	Ethernet device's name.
> +  @return
> + *   - Slot in the rte_dev_devices array for attached device;

Yes, that's what it returns on success. You also need to add the case
when it fails.

> + */
> +struct rte_eth_dev *rte_eth_dev_attach_secondary(const char *name);
> +
> +/**
> + * @internal
>   * Release the specified ethdev port.
>   *
>   * @param eth_dev
> diff --git a/lib/librte_ether/rte_ether_version.map b/lib/librte_ether/rte_ether_version.map
> index c6c9d0d..f8bf2ee 100644
> --- a/lib/librte_ether/rte_ether_version.map
> +++ b/lib/librte_ether/rte_ether_version.map
> @@ -152,5 +152,6 @@ DPDK_17.02 {
>  	rte_flow_flush;
>  	rte_flow_query;
>  	rte_flow_validate;
> +	rte_eth_dev_attach_secondary;
>  
>  } DPDK_16.11;

17.02 is released, you should add a new table for 17.05 and add it there.


Besides, I would suggest you to split this patch into two:

- one for exporting rte_eth_dev_attach_secondary
- another for fixing the bug

	--yliu