On Tue, 2007-09-25 at 20:32 +0200, Michael S. Tsirkin wrote: > > Quoting Ralph Campbell <[EMAIL PROTECTED]>: > > Subject: Re: [PATCH 1/11] IB/ipoib: high dma support ... > > > I got the impression that all supported IB devices support dma-ing > > > to/from memory > 4GB. Perhaps other vendors can comment. > > > > The QLogic HCAs don't support DMA to or from the physical memory > > for the verbs Lkey/Rkey memory regions. The whole reason I added > > the ib_dma_*() functions was so to avoid ib_ipoib, etc. from > > calling dma_*() directly and passing a physical address as the > > offset in the posted work requests. > > What happens instead, is that ib_dma_*() returns a kernel virtual > > address which is passed in the work request and the driver copies > > the data to/from the HW as needed. > > So, in order to support HIGHMEM, I would need to change the > > ipath_dma_*() functions to call kmap()/kunmap() for HIGHMEM pages. > > I'm sure there would be all kinds of performance and coding issues > > around doing this. > > So, we need some kind of HIGHDMA capability flag?
Yes, A HIGHDMA capability flag would be useful. I think that setting NETIF_F_HIGHDMA for ib_ipoib is a NOP for the systems QLogic supports (i.e., only 64-bit kernels) but that could change. Better to plan ahead. _______________________________________________ general mailing list [email protected] http://lists.openfabrics.org/cgi-bin/mailman/listinfo/general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
