Re: [dpdk-dev] [PATCH v2 5/7] mem: modify error message for DMA mask check

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

On Mon, Nov 5, 2018 at 3:12 PM Burakov, Anatoly <anatoly.burakov@intel.com>
wrote:

> On 05-Nov-18 10:13 AM, Alejandro Lucero wrote:
> > On Mon, Nov 5, 2018 at 10:01 AM Li, WenjieX A <wenjiex.a.li@intel.com>
> > wrote:
> >
> >> 1. With GCC32, testpmd could not startup without '--iova-mode pa'.
> >> ./i686-native-linuxapp-gcc/app/testpmd -c f -n 4 -- -i
> >> The output is:
> >> EAL: Detected 16 lcore(s)
> >> EAL: Detected 1 NUMA nodes
> >> EAL: Multi-process socket /var/run/dpdk/rte/mp_socket
> >> EAL: Some devices want iova as va but pa will be used because.. EAL: few
> >> device bound to UIO
> >> EAL: No free hugepages reported in hugepages-1048576kB
> >> EAL: Probing VFIO support...
> >> EAL: VFIO support initialized
> >> EAL: wrong dma mask size 48 (Max: 31)
> >> EAL: alloc_pages_on_heap(): couldn't allocate memory due to IOVA
> exceeding
> >> limits of current DMA mask
> >> error allocating rte services array
> >> EAL: FATAL: rte_service_init() failed
> >> EAL: rte_service_init() failed
> >> PANIC in main():
> >> Cannot init EAL
> >> 5: [./i686-native-linuxapp-gcc/app/testpmd(+0x95fda) [0x56606fda]]
> >> 4: [/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf6) [0xf74d1276]]
> >> 3: [./i686-native-linuxapp-gcc/app/testpmd(main+0xf21) [0x565fcee1]]
> >> 2: [./i686-native-linuxapp-gcc/app/testpmd(__rte_panic+0x3d)
> [0x565edc68]]
> >> 1: [./i686-native-linuxapp-gcc/app/testpmd(rte_dump_stack+0x33)
> >> [0x5675f333]]
> >> Aborted
> >>
> >> 2. With '--iova-mode pa', testpmd could startup.
> >> 3. With GCC64, there is no such issue.
> >> Thanks!
> >>
> >>
> > Does 32 bits support require IOMMU? It would be a surprise. If there is
> no
> > IOMMU hardware, no dma mask should be there at all.
>
> IOMMU is supported on 32-bits, however limited the address space might
> be. Maybe limit IOMMU width to RTE_MIN(31, value) bits for everything on
> 32-bit?
>
>
If IOMMU is supported in 32 bits, then the DMA mask check should not be
happening. AFAIK, the IOMMU hardware addressing limitations is a problem
only in 64 bits systems. The worst situation I have head of is 39 bits for
virtualized IOMMU with QEMU.

I would prefer not to invoke rte_mem_set_dma_mask for 32 bits system for
the Intel IOMMU case. The only other dma mask client is the NFP PMD and we
do not support 32 bits systems.



> --
> Thanks,
> Anatoly
>