Re: [PATCH v2] bus/pci: don't open uio device in secondary process

[Chenbo Xia <chenbox@nvidia.com>]

> On Aug 29, 2024, at 16:57, Konrad Sztyber <konrad.sztyber@intel.com> wrote:
> 
> External email: Use caution opening links or attachments
> 
> 
> The uio_pci_generic driver clears the bus master bit when the device
> file is closed. So, when the secondary process terminates after probing
> a device, that device becomes unusable in the primary process.
> 
> To avoid that, the device file is now opened only in the primary
> process. The commit that introduced this regression, 847d78fb9530
> ("bus/pci: fix FD in secondary process"), only mentioned enabling access
> to config space from secondary process, which still works, as it doesn't
> rely on the device file.
> 
> Fixes: 847d78fb9530 ("bus/pci: fix FD in secondary process")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Konrad Sztyber <konrad.sztyber@intel.com>
> ---
> drivers/bus/pci/linux/pci_uio.c | 27 +++++++++++++++------------
> 1 file changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/bus/pci/linux/pci_uio.c b/drivers/bus/pci/linux/pci_uio.c
> index 4c1d3327a9..5c4ba8098c 100644
> --- a/drivers/bus/pci/linux/pci_uio.c
> +++ b/drivers/bus/pci/linux/pci_uio.c
> @@ -232,18 +232,6 @@ pci_uio_alloc_resource(struct rte_pci_device *dev,
>                       loc->domain, loc->bus, loc->devid, loc->function);
>               return 1;
>       }
> -       snprintf(devname, sizeof(devname), "/dev/uio%u", uio_num);
> -
> -       /* save fd */
> -       fd = open(devname, O_RDWR);
> -       if (fd < 0) {
> -               PCI_LOG(ERR, "Cannot open %s: %s", devname, strerror(errno));
> -               goto error;
> -       }
> -
> -       if (rte_intr_fd_set(dev->intr_handle, fd))
> -               goto error;
> -
>       snprintf(cfgname, sizeof(cfgname),
>                       "/sys/class/uio/uio%u/device/config", uio_num);
> 
> @@ -273,6 +261,21 @@ pci_uio_alloc_resource(struct rte_pci_device *dev,
>       if (rte_eal_process_type() != RTE_PROC_PRIMARY)
>               return 0;
> 
> +       /*
> +        * the uio_pci_generic driver clears the bus master enable bit when the device file is
> +        * closed, so open it only in the primary process
> +        */
> +       snprintf(devname, sizeof(devname), "/dev/uio%u", uio_num);
> +       /* save fd */
> +       fd = open(devname, O_RDWR);
> +       if (fd < 0) {
> +               PCI_LOG(ERR, "Cannot open %s: %s", devname, strerror(errno));
> +               goto error;
> +       }
> +
> +       if (rte_intr_fd_set(dev->intr_handle, fd))
> +               goto error;
> +
>       /* allocate the mapping details for secondary processes*/
>       *uio_res = rte_zmalloc("UIO_RES", sizeof(**uio_res), 0);
>       if (*uio_res == NULL) {
> --
> 2.45.0
> 

Reviewed-by: Chenbo Xia <chenbox@nvidia.com>