[openib-general] [PATCH 5 of 5] IB/mthca: give reserved MTTs a separate cache line

[Michael S. Tsirkin]

> >  > +	/* CPU writes to non-reserved MTTs, while HCA might DMA to reserved mtts */
> >  > +	mdev->limits.reserved_mtts = max(dma_get_cache_alignment() / (int)sizeof(u64),
> >  > +					 mdev->limits.reserved_mtts);
> > 
> > I don't follow this -- first of all, what guarantee is there that the
> > reserved MTTs end on a cacheline boundary just because they take up
> > more than a single cacheline?  It seems this should really be using
> > ALIGN() somehow.
> 
> Actually, I think that we really must have each of the tables start at
> ICM-page aligned addresses. I think this happened to work fine so far
> as profile was hard-coded, but with new module option code
> this might not be the case anymore.
> 
> Since we access some of them from CPU and some from hardware, we really need
> them different tables separate dma cache lines too.  ICM-page alignment probably
> gives this to us for free, but the following patch makes this assumption explicit.
> 
> Pls review.
> 
> Warning: untested patch.
> 
> Signed-off-by: Michael S. Tsirkin <mst at mellanox.co.il>

I see now this is broken. Working on an updated patch.

-- 
MST