[openib-general] Re: [PATCHv2 1/2] resend: mthca support for max_map_per_fmr device attribute

[Roland Dreier]

I had a chance to look at this, and I don't believe it is precisely
correct for mem-free HCAs with the current FMR implementation.

 > +	/* on memfull HCA an FMR can be remapped 2^B - 1 times where B < 32 is
 > +	 * the number of bits which are not used for MPT addressing, on memfree
 > +	 * HCA B=8 so an FMR can be remapped 255 times.
 > +	 */
 > +	if(!mthca_is_memfree(mdev))
 > +		props->max_map_per_fmr = (1 << (32 -
 > +					long_log2(mdev->limits.num_mpts))) - 1;
 > +	else
 > +		props->max_map_per_fmr = (1 << 8) - 1;

Look at mthca_arbel_map_phys_fmr().  The question is how often key
will repeat after being indexed, and when MTHCA_FLAG_SINAI_OPT is not
set, then the same increment is used in the mem-free case as in the
Tavor case.

So I think the code I quoted should really be:

	if (dev->mthca_flags & MTHCA_FLAG_SINAI_OPT)
		props->max_map_per_fmr = (1 << (32 -
					long_log2(mdev->limits.num_mpts))) - 1;
	else
		props->max_map_per_fmr = (1 << 8) - 1;

Do you agree?  If so I can fix this patch up myself and apply it.

 - R.