Re: [dpdk-dev] [PATCH v2 0/6] use IOVAs check based on DMA mask

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 03-Jul-18 1:09 PM, Alejandro Lucero wrote:
> This patchset adds, mainly, a check for ensuring IOVAs are within a
> restricted range due to addressing limitations with some devices. There
> are two known cases: NFP and IOMMU VT-d emulation.
> 
> With this check IOVAs out of range are detected and PMDs can abort
> initialization. For the VT-d case, IOVA VA mode is allowed as long as
> IOVAs are within the supported range, avoiding to forbid IOVA VA by
> default.
> 
> For the addressing limitations known cases, there are just 40(NFP) or
> 39(VT-d) bits for handling IOVAs. When using IOVA PA, those limitations
> imply 1TB(NFP) or 512M(VT-d) as upper limits, which is likely enough for
> most systems. With machines using more memory, the added check will
> ensure IOVAs within the range.
> 
> With IOVA VA, and because the way the Linux kernel serves mmap calls
> in 64 bits systems, 39 or 40 bits are not enough. It is possible to
> give an address hint with a lower starting address than the default one
> used by the kernel, and then ensuring the mmap uses that hint or hint plus
> some offset. With 64 bits systems, the process virtual address space is
> large enoguh for doing the hugepages mmaping within the supported range
> when those addressing limitations exist. This patchset also adds a change
> for using such a hint making the use of IOVA VA a more than likely
> possibility when there are those addressing limitations.
> 
> The check is not done by default but just when it is required. This
> patchset adds the check for NFP initialization and for setting the IOVA
> mode is an emulated VT-d is detected.
> 
> This patchset applies on 17.11.3.
> 
> Similar changes will be submitted to main DPDK branch soon.
> 
> v2:
>   - add get_addr_hint function
>   - call munmap when hint given and not used by mmap
>   - create dma mask in one step
>   - refactor logs
> 
> 

General comment - new API's should probably be added to the .map files?

-- 
Thanks,
Anatoly