Re: [dpdk-dev] [PATCH] eal: fix secondary process segfault on multipe virtio devices

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

HI Thomas,


> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas@monjalon.net]
> Sent: Saturday, July 1, 2017 10:10 PM
> To: Tan, Jianfeng
> Cc: dev@dpdk.org; yuanhan.liu@linux.intel.com;
> maxime.coquelin@redhat.com
> Subject: Re: [dpdk-dev] [PATCH] eal: fix secondary process segfault on
> multipe virtio devices
> 
> 02/06/2017 18:20, Jianfeng Tan:
> > Suppose we have 2 virtio devices for a VM, with only the first one,
> > virtio0, binding to igb_uio. Start a primary DPDK process, driving
> > only virtio0. Then start a secondary DPDK process, it encounters
> > segfault at eth_virtio_dev_init() because hw is NULL, when trying
> > to initialize the 2nd virtio devices.
> >     1539                    if (!hw->virtio_user_dev) {
> >
> > We could add a precheck to return error when hw is NULL. But the
> > root cause is that virtio devices which are not driven by the primary
> > process are not exluded by secondary eal probe function.
> >
> > To support legacy virtio devices bound to none kernel driver, we
> > removed RTE_PCI_DRV_NEED_MAPPING in
> > commit 962cf902e6eb ("pci: export device mapping functions").
> > At the boot of primary process, ether dev is allocated in rte_eth_devices
> > array, rte_eth_dev_data is also allocated in rte_eth_dev_data array; then
> > probe function fails; and ether dev is released. However, the entry in
> > rte_eth_dev_data array is not cleared. Then we start secondary process,
> > and try to attach the virtio device that not used in primary process,
> > the field, dev_private (or hw), in rte_eth_dev_data, is NULL.
> >
> > To fail the dev attach, we need to clear the field, name, when we
> > release any ether devices in primary, so that below loop in
> > rte_eth_dev_attach_secondary() will not find any matched names.
> >         for (i = 0; i < RTE_MAX_ETHPORTS; i++) {
> >                 if (strcmp(rte_eth_dev_data[i].name, name) == 0)
> >                         break;
> >         }
> >
> > Fixes: 6d890f8ab512 ("Fixes: net/virtio: fix multiple process support")
> 
> It probably needs to be Cc: stable@dpdk.org
> 
> > Reported-by: Reshma Pattan <reshma.pattan@intel.com>
> > Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
> > ---
> [...]
> >  	eth_dev->data->dev_private = NULL;
> >
> > +	/* Secondary process will use this field, name, for secondary attach,
> > +	 * clear this field to avoid attaching any released ports in primary.
> > +	 */
> > +	memset(eth_dev->data->name, 0, RTE_ETH_NAME_MAX_LEN);
> 
> I think it may be sufficient to set an empty string:
> eth_dev->data->name = '\0';

Thank you for the advice. And a new version has been sent.

Thanks,
Jianfeng