[dpdk-dev] [PATCH v2 0/5] use IOVAs check based on DMA mask

Alejandro Lucero alejandro.lucero at netronome.com
Tue Oct 2 18:33:06 CEST 2018

As I was told, I sent this patchset early September (actually it was still
October) for making it for 18.11.

I wonder if this will be applied when doing the integration phase or it
will need to wait until 19.02.

On Fri, Aug 31, 2018 at 1:51 PM Alejandro Lucero <
alejandro.lucero at netronome.com> wrote:

> I sent a patchset about this to be applied on 17.11 stable. The memory
> code has had main changes since that version, so here it is the patchset
> adjusted to current master repo.
> 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. Also, because the recent patchset
> adding dynamic memory allocation, the check is also invoked for ensuring
> the new memsegs are within the required range.
> This patchset could be applied to stable 18.05.
> v2:
>  - fix problem with max dma mask definition

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