On 12/5/06, David Miller <[email protected]> wrote:
From: "Matt Reimer" <[email protected]>
Date: Mon, 4 Dec 2006 23:38:13 -0800
> In light of James Bottomsley's commit[1] declaring that kmap() and
> friends now have to take care of coherency issues, is the patch "mm:
> D-cache aliasing issue in cow_user_page"[2] correct, or could it
> potentially cause a slowdown by calling flush_dcache_page() a second
> time (i.e. once in an architecture-specific kmap() implementation, and
> once in cow_user_page())?
kmap() is a NOP unless HIGHMEM is configured.
Therefore, it cannot possibly take care of D-cache aliasing issues
across the board.
Right, but isn't he declaring that each architecture needs to take
care of this? So, say, on ARM we'd need to make kunmap() not a NOP and
call flush_dcache_page() ?
Matt
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