Re: [dpdk-dev] [PATCH] eal: pick IOVA as PA if IOMMU is not available

[David Marchand <david.marchand@redhat.com>]

On Wed, Jul 24, 2019 at 6:46 PM Anatoly Burakov
<anatoly.burakov@intel.com> wrote:
>
> When IOMMU is not available, /sys/kernel/iommu_groups will not be
> populated. This is happening since at least 3.6 when VFIO support
> was added. If the directory is empty, EAL should not pick IOVA as
> VA as the default IOVA mode.
>
> We also assume that VFIO equals IOMMU, so if VFIO support is not
> compiled, we always assume IOMMU support is not available.

Not sure I agree with this statement.
What about unknown (from eal pov) kernel drivers?


>
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
> ---
>  lib/librte_eal/linux/eal/eal.c      | 11 ++++++--
>  lib/librte_eal/linux/eal/eal_vfio.c | 39 +++++++++++++++++++++++++++++
>  lib/librte_eal/linux/eal/eal_vfio.h |  2 ++
>  3 files changed, 50 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_eal/linux/eal/eal.c b/lib/librte_eal/linux/eal/eal.c
> index 34db78753..584f97a96 100644
> --- a/lib/librte_eal/linux/eal/eal.c
> +++ b/lib/librte_eal/linux/eal/eal.c
> @@ -1061,8 +1061,15 @@ rte_eal_init(int argc, char **argv)
>                 enum rte_iova_mode iova_mode = rte_bus_get_iommu_class();
>
>                 if (iova_mode == RTE_IOVA_DC) {
> -                       iova_mode = RTE_IOVA_VA;
> -                       RTE_LOG(DEBUG, EAL, "Buses did not request a specific IOVA mode, select IOVA as VA mode.\n");
> +                       /* if we have an IOMMU, pick IOVA as VA mode */
> +                       if (vfio_iommu_enabled()) {
> +                               iova_mode = RTE_IOVA_VA;
> +                               RTE_LOG(DEBUG, EAL, "Buses did not request a specific IOVA mode, selecting IOVA as VA mode.\n");
> +                       } else {
> +                               iova_mode = RTE_IOVA_PA;
> +                               RTE_LOG(DEBUG, EAL, "Buses did not request a specific IOVA mode, but IOMMU is not available.\n");
> +                               RTE_LOG(DEBUG, EAL, "Selecting IOVA as PA mode.\n");
> +                       }

Here, since the buses don't care, we can check for physical address
availability.


-- 
David Marchand