Re: [dpdk-dev] [PATCH] vfio: correct system call error checking

["Richardson, Bruce" <bruce.richardson@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Neil Horman
> Sent: Tuesday, June 17, 2014 12:04 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH] vfio: correct system call error checking
> 
> Noticed today that ioctl error code return checking was incorrect in some of the
> vfio code.  ioctl can return a negative value if the system detects an error
> before the target device/driver can produce a return code.  The dpdk vfio code
> only checks specfically for the values that it expects, which leaves it open to
> accepting unexpected error codes as success.  For instance, if the vfio layer
> noted that the iommu driver hadn't finished registering yet, it would return an
> -EINVAL error code, but the dpdk would accept that as success, becuase it
> wasn't
> 0.
> 
> Fix this to specifically check for < 0 error codes
> 
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> CC: Thomas Monjalon <thomas.monjalon@6wind.com>
> ---
>  lib/librte_eal/linuxapp/eal/eal_pci_vfio.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c
> b/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c
> index 4de6061..65aa8ad 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c
> @@ -319,16 +319,16 @@ pci_vfio_get_container_fd(void)
> 
>  		/* check VFIO API version */
>  		ret = ioctl(vfio_container_fd, VFIO_GET_API_VERSION);
> -		if (ret != VFIO_API_VERSION) {
> -			RTE_LOG(ERR, EAL, "  unknown VFIO API version!\n");
> +		if ((ret < 0) || (ret != VFIO_API_VERSION)) {
> +			RTE_LOG(ERR, EAL, "  unknown VFIO API version! errno
> = %d\n", errno);
>  			close(vfio_container_fd);
>  			return -1;
>  		}

Not sure how this change improves things, since the existing check will already trigger an error on all values <0. Can you please clarify why you think this needs to be changed?

> 
>  		/* check if we support IOMMU type 1 */
>  		ret = ioctl(vfio_container_fd, VFIO_CHECK_EXTENSION,
> VFIO_TYPE1_IOMMU);
> -		if (!ret) {
> -			RTE_LOG(ERR, EAL, "  unknown IOMMU driver!\n");
> +		if (ret <= 0) {
> +			RTE_LOG(ERR, EAL, "  unknown IOMMU driver! errno =
> %d\n", errno);
>  			close(vfio_container_fd);
>  			return -1;
>  		}

Ack on this change part. The previously code was incorrect according to what I read in the docs for VFIO.

/Bruce