Re: [PATCH] wifi: iwlwifi: correctly lookup DMA address in SG table

[Kalle Valo <kvalo@kernel.org>]

Benjamin Berg <benjamin@sipsolutions.net> writes:

> From: Benjamin Berg <benjamin.berg@intel.com>
>
> The code to lookup the scatter gather table entry assumed that it was
> possible to use sg_virt() in order to lookup the DMA address in a mapped
> scatter gather table. However, this assumption is incorrect as the DMA
> mapping code may merge multiple entries into one. In that case, the DMA
> address space may have e.g. two consecutive pages which is correctly
> represented by the scatter gather list entry, however the virtual
> addresses for these two pages may differ and the relationship cannot be
> resolved anymore.
>
> Avoid this problem entirely by working with the offset into the mapped
> area instead of using virtual addresses. With that we only use the DMA
> length and DMA address from the scatter gather list entries. The
> underlying DMA/IOMMU code is therefore free to merge two entries into
> one even if the virtual addresses space for the area is not continuous.
>
> Fixes: 90db50755228 ("wifi: iwlwifi: use already mapped data when TXing an AMSDU")
> Reported-by: Chris Bainbridge <chris.bainbridge@gmail.com>
> Closes: https://lore.kernel.org/r/ZrNRoEbdkxkKFMBi@debian.local
> Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>

Reminder to myself: if this passes the tests it should go to wireless
tree. Assigned the patch to me on patchwork.

Miri, if you agree please give an Acked-by.

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