Re: [PATCH V4 1/5] drivers/bus: restore driver assignment at front of probing

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 12/6/2022 9:26 AM, Huisong Li wrote:
> The driver assignment was moved back at the end of the device probing
> because there is no something to use rte_driver during the phase of
> probing. See commit 391797f04208 ("drivers/bus: move driver assignment
> to end of probing")
> 
> However, it is necessary for probing callback to reference rte_driver
> before probing. For example, probing callback may call some APIs which
> access the rte_pci_driver::driver by the device::driver pointer to get
> driver information. In this case, a segment fault will occur in probing
> callback if there is not this assignment.
> 

Probing callback gets driver as parameter, so callback function can
access it via 'drv->driver', is there a specific usecase that
'dev->device->driver' needs to be accessed explicitly?

I assume this is related to coming patches that setting up device in
testpmd event callback, but can you please clarify exact need.

> Further, some comments in code need to be updated if we do that. The
> driver pointer in rte_device is set before probing and needs to be reset
> if probing failed. And rte_dev_is_probed can not be called inside probing.
> 
> Fixes: 391797f04208 ("drivers/bus: move driver assignment to end of probing")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Huisong Li <lihuisong@huawei.com>
> ---
>  drivers/bus/auxiliary/auxiliary_common.c |  9 +++++++--
>  drivers/bus/dpaa/dpaa_bus.c              |  9 +++++++--
>  drivers/bus/fslmc/fslmc_bus.c            |  8 +++++++-
>  drivers/bus/ifpga/ifpga_bus.c            | 12 +++++++++---
>  drivers/bus/pci/pci_common.c             |  9 +++++++--
>  drivers/bus/vdev/vdev.c                  | 10 ++++++++--
>  drivers/bus/vmbus/vmbus_common.c         |  9 +++++++--
>  7 files changed, 52 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/bus/auxiliary/auxiliary_common.c b/drivers/bus/auxiliary/auxiliary_common.c
> index ff1369353a..13cb3fe0f8 100644
> --- a/drivers/bus/auxiliary/auxiliary_common.c
> +++ b/drivers/bus/auxiliary/auxiliary_common.c
> @@ -132,16 +132,21 @@ rte_auxiliary_probe_one_driver(struct rte_auxiliary_driver *drv,
>  	}
>  
>  	dev->driver = drv;
> +	/*
> +	 * Reference rte_driver before probing so as to this pointer can
> +	 * be used to get driver information in case of segment fault in
> +	 * probing callback.
> +	 */
> +	dev->device.driver = &drv->driver;
>  
>  	AUXILIARY_LOG(INFO, "Probe auxiliary driver: %s device: %s (NUMA node %i)",
>  		      drv->driver.name, dev->name, dev->device.numa_node);
>  	ret = drv->probe(drv, dev);
>  	if (ret != 0) {
>  		dev->driver = NULL;
> +		dev->device.driver = NULL;
>  		rte_intr_instance_free(dev->intr_handle);
>  		dev->intr_handle = NULL;
> -	} else {
> -		dev->device.driver = &drv->driver;
>  	}
>  
>  	return ret;
> diff --git a/drivers/bus/dpaa/dpaa_bus.c b/drivers/bus/dpaa/dpaa_bus.c
> index e57159f5d8..f1b817e58c 100644
> --- a/drivers/bus/dpaa/dpaa_bus.c
> +++ b/drivers/bus/dpaa/dpaa_bus.c
> @@ -693,17 +693,22 @@ rte_dpaa_bus_probe(void)
>  			    (dev->device.devargs &&
>  			     dev->device.devargs->policy == RTE_DEV_BLOCKED))
>  				continue;
> -
> +			/*
> +			 * Reference rte_driver before probing so as to this
> +			 * pointer can be used to get driver information in case
> +			 * of segment fault in probing callback.
> +			 */
> +			dev->device.driver = &drv->driver;
>  			if (probe_all ||
>  			    (dev->device.devargs &&
>  			     dev->device.devargs->policy == RTE_DEV_ALLOWED)) {
>  				ret = drv->probe(drv, dev);
>  				if (ret) {
> +					dev->device.driver = NULL;
>  					DPAA_BUS_ERR("unable to probe:%s",
>  						     dev->name);
>  				} else {
>  					dev->driver = drv;
> -					dev->device.driver = &drv->driver;
>  				}
>  			}
>  			break;
> diff --git a/drivers/bus/fslmc/fslmc_bus.c b/drivers/bus/fslmc/fslmc_bus.c
> index 57bfb5111a..4bc0c6d3d4 100644
> --- a/drivers/bus/fslmc/fslmc_bus.c
> +++ b/drivers/bus/fslmc/fslmc_bus.c
> @@ -471,15 +471,21 @@ rte_fslmc_probe(void)
>  				continue;
>  			}
>  
> +			/*
> +			 * Reference rte_driver before probing so as to this
> +			 * pointer can be used to get driver information in case
> +			 * of segment fault in probing callback.
> +			 */
> +			dev->device.driver = &drv->driver;
>  			if (probe_all ||
>  			   (dev->device.devargs &&
>  			    dev->device.devargs->policy == RTE_DEV_ALLOWED)) {
>  				ret = drv->probe(drv, dev);
>  				if (ret) {
> +					dev->device.driver = NULL;
>  					DPAA2_BUS_ERR("Unable to probe");
>  				} else {
>  					dev->driver = drv;
> -					dev->device.driver = &drv->driver;
>  				}
>  			}
>  			break;
> diff --git a/drivers/bus/ifpga/ifpga_bus.c b/drivers/bus/ifpga/ifpga_bus.c
> index bb943b58b5..5f23446f41 100644
> --- a/drivers/bus/ifpga/ifpga_bus.c
> +++ b/drivers/bus/ifpga/ifpga_bus.c
> @@ -293,13 +293,19 @@ ifpga_probe_one_driver(struct rte_afu_driver *drv,
>  
>  	/* reference driver structure */
>  	afu_dev->driver = drv;
> +	/*
> +	 * Reference rte_driver before probing so as to this pointer can
> +	 * be used to get driver information in case of segment fault in
> +	 * probing callback.
> +	 */
> +	afu_dev->device.driver = &drv->driver;
>  
>  	/* call the driver probe() function */
>  	ret = drv->probe(afu_dev);
> -	if (ret)
> +	if (ret) {
>  		afu_dev->driver = NULL;
> -	else
> -		afu_dev->device.driver = &drv->driver;
> +		afu_dev->device.driver = NULL;
> +	}
>  
>  	return ret;
>  }
> diff --git a/drivers/bus/pci/pci_common.c b/drivers/bus/pci/pci_common.c
> index bc3a7f39fe..efaa1792e9 100644
> --- a/drivers/bus/pci/pci_common.c
> +++ b/drivers/bus/pci/pci_common.c
> @@ -302,6 +302,12 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
>  				return ret;
>  			}
>  		}
> +		/*
> +		 * Reference rte_driver before probing so as to this pointer can
> +		 * be used to get driver information in case of segment fault in
> +		 * probing callback.
> +		 */
> +		dev->device.driver = &dr->driver;
>  	}
>  
>  	RTE_LOG(INFO, EAL, "Probe PCI driver: %s (%x:%x) device: "PCI_PRI_FMT" (socket %i)\n",
> @@ -314,6 +320,7 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
>  		return ret; /* no rollback if already succeeded earlier */
>  	if (ret) {
>  		dev->driver = NULL;
> +		dev->device.driver = NULL;
>  		if ((dr->drv_flags & RTE_PCI_DRV_NEED_MAPPING) &&
>  			/* Don't unmap if device is unsupported and
>  			 * driver needs mapped resources.
> @@ -325,8 +332,6 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
>  		dev->vfio_req_intr_handle = NULL;
>  		rte_intr_instance_free(dev->intr_handle);
>  		dev->intr_handle = NULL;
> -	} else {
> -		dev->device.driver = &dr->driver;
>  	}
>  
>  	return ret;
> diff --git a/drivers/bus/vdev/vdev.c b/drivers/bus/vdev/vdev.c
> index 41bc07dde7..2e3f0f2e12 100644
> --- a/drivers/bus/vdev/vdev.c
> +++ b/drivers/bus/vdev/vdev.c
> @@ -207,9 +207,15 @@ vdev_probe_all_drivers(struct rte_vdev_device *dev)
>  		return -1;
>  	}
>  
> +	/*
> +	 * Reference rte_driver before probing so as to this pointer can
> +	 * be used to get driver information in case of segment fault in
> +	 * probing callback.
> +	 */
> +	dev->device.driver = &driver->driver;
>  	ret = driver->probe(dev);
> -	if (ret == 0)
> -		dev->device.driver = &driver->driver;
> +	if (ret != 0)
> +		dev->device.driver = NULL;
>  	return ret;
>  }
>  
> diff --git a/drivers/bus/vmbus/vmbus_common.c b/drivers/bus/vmbus/vmbus_common.c
> index 8d32d66504..feb1651984 100644
> --- a/drivers/bus/vmbus/vmbus_common.c
> +++ b/drivers/bus/vmbus/vmbus_common.c
> @@ -110,6 +110,12 @@ vmbus_probe_one_driver(struct rte_vmbus_driver *dr,
>  
>  	/* reference driver structure */
>  	dev->driver = dr;
> +	/*
> +	 * Reference rte_driver before probing so as to this pointer can
> +	 * be used to get driver information in case of segment fault in
> +	 * probing callback.
> +	 */
> +	dev->device.driver = &dr->driver;
>  
>  	if (dev->device.numa_node < 0 && rte_socket_count() > 1)
>  		VMBUS_LOG(INFO, "Device %s is not NUMA-aware", guid);
> @@ -119,9 +125,8 @@ vmbus_probe_one_driver(struct rte_vmbus_driver *dr,
>  	ret = dr->probe(dr, dev);
>  	if (ret) {
>  		dev->driver = NULL;
> +		dev->device.driver = NULL;
>  		rte_vmbus_unmap_device(dev);
> -	} else {
> -		dev->device.driver = &dr->driver;
>  	}
>  
>  	return ret;