Re: [dpdk-dev] [PATCH] memory: do not use base-virtaddr in secondary processes

[Alejandro Lucero <alejandro.lucero@netronome.com>]

On Mon, Jun 18, 2018 at 8:53 PM, Dariusz Stojaczyk <
dariuszx.stojaczyk@intel.com> wrote:

> Since secondary process' address space is highly dictated
> by the primary process' mappings, it doesn't make much
> sense to use base-virtaddr for secondary processes.
>
> This patch is intended to fix PCI resource mapping
> in secondary processes using the same base-virtaddr
> as their primary processes. PCI uses the end of the hugepage
> memory area to map all resources. [pci_find_max_end_va()]
> It works for primary processes, but can't be mapped 1:1
> by secondary ones, as the same addresses are currently always
> occupied by shadow memseg lists, which were created with
> eal_get_virtual_area(NULL, ...).
>
>
Should not be better to handle these allocations being aware about the
problem for secondary processes?

I do not know exactly what are the (other) reasons behind base-virtaddr,
but it turns out NFP requires this to be used when DPDK apps executed by
non-root users.

I'm working on a RFC for handling our specific case, that could also be
required for other devices, and this change would make the NFP unusable for
the secondary processes.



> ```
> PRIMARY PROCESS
> 0x6e00e00000    388K rw-s- fbarray_memseg-2048k-1-3
> 0x6e01000000 16777216K r----   [ anon ]
> 0x7201000000     16K rw-s- resource0
>
> SECONDARY PROCESS
> 0x6e00e00000    388K rw-s- fbarray_memseg-2048k-1-3
> 0x6e01000000 16777216K r----   [ anon ]
> 0x7201000000      4K rw-s- fbarray_memseg-1048576k-0-0_203213
> ```
>
> Fixes: 524e43c2ad9a ("mem: prepare memseg lists for multiprocess sync")
> Cc: anatoly.burakov@intel.com
> Cc: stable@dpdk.org
>
> Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
> ---
>  lib/librte_eal/common/eal_common_memory.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/librte_eal/common/eal_common_memory.c
> b/lib/librte_eal/common/eal_common_memory.c
> index 53d9b51..6c47e11 100644
> --- a/lib/librte_eal/common/eal_common_memory.c
> +++ b/lib/librte_eal/common/eal_common_memory.c
> @@ -56,7 +56,8 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
>         allow_shrink = (flags & EAL_VIRTUAL_AREA_ALLOW_SHRINK) > 0;
>         unmap = (flags & EAL_VIRTUAL_AREA_UNMAP) > 0;
>
> -       if (next_baseaddr == NULL && internal_config.base_virtaddr != 0)
> +       if (next_baseaddr == NULL && internal_config.base_virtaddr != 0 &&
> +                       rte_eal_process_type() == RTE_PROC_PRIMARY)
>                 next_baseaddr = (void *) internal_config.base_virtaddr;
>
>         if (requested_addr == NULL && next_baseaddr) {
> --
> 2.7.4
>
>