On Wed, Apr 22, 2015 at 02:53:11PM -0400, Doug Ledford wrote: > On Wed, 2015-04-22 at 10:17 -0600, Jason Gunthorpe wrote: > > On Wed, Apr 22, 2015 at 05:23:28PM +0200, Luis R. Rodriguez wrote: > > > On Tue, Apr 21, 2015 at 11:39:39PM -0600, Jason Gunthorpe wrote: > > > > On Wed, Apr 22, 2015 at 01:39:07AM +0200, Luis R. Rodriguez wrote: > > > > > > Mike, do you think the time is right to just remove the iPath driver? > > > > > > > > > > With PAT now being default the driver effectively won't work > > > > > with write-combining on modern kernels. Even if systems are old > > > > > they likely had PAT support, when upgrading kernels PAT will work > > > > > but write-combing won't on ipath. > > > > > > > > Sorry, do you mean the driver already doesn't get WC? Or do you mean > > > > after some more pending patches are applied? > > > > > > No, you have to consider the system used and the effects of calls used > > > on the driver in light of this table: > > > > So, just to be clear: > > > > At some point Linux started setting the PAT bits during > > ioremap_nocache, which overrides MTRR, and at that point the driver > > became broken on all PAT capable systems? > > > > Not only that, but we've only just noticed it now, and no user ever > > complained? > > > > So that means either no users exist, or all users are on non-PAT > > systems? > > > > This driver only works on x86-64 systems. Are there any x86-64 systems > > that are not PAT capable? IIRC even the first Opteron had PAT, but my > > memory is fuzzy from back then :| > > > > > Another option in order to enable this type of checks at run time > > > and still be able to build the driver on standard distributions and > > > just prevent if from loading on PAT systems is to have some code in > > > place which would prevent the driver from loading if PAT was > > > enabled, this would enable folks to disable PAT via a kernel command > > > line option, and if that was used then the driver probe would > > > complete. > > > > This seems like a reasonble option to me. At the very least we might > > learn if anyone is still using these cards. > > > > I'd also love to remove the driver if it turns out there are actually > > no users. qib substantially replaces it except for a few very old > > cards. > > To be precise, the split is that ipath powers the old HTX bus cards that > only work in AMD systems, Do those systems have PAT support? CAn anyone check if PAT is enabled if booted on a recent kernel? Luis -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
