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Date: Sun, 24 Jan 2016 10:40:56 +0100 From: Borislav Petkov <bp@...e.de> To: Dan Williams <dan.j.williams@...el.com> Cc: Sudip Mukherjee <sudipm.mukherjee@...il.com>, Christoph Hellwig <hch@....de>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>, Jerome Glisse <j.glisse@...il.com>, markk@...ra.co.uk, Joerg Roedel <jroedel@...e.de>, lkml <linux-kernel@...r.kernel.org>, linux-mm@...ck.org Subject: Re: [BUG] Devices breaking due to CONFIG_ZONE_DEVICE + linux-mm On Fri, Jan 22, 2016 at 10:15:17PM -0800, Dan Williams wrote: > On Fri, Jan 22, 2016 at 9:47 PM, Dan Williams <dan.j.williams@...el.com> wrote: > > On Fri, Jan 22, 2016 at 8:46 PM, Sudip Mukherjee > > <sudipm.mukherjee@...il.com> wrote: > >> Hi All, > >> Commit 033fbae988fc ("mm: ZONE_DEVICE for "device memory"") has > >> introduced CONFIG_ZONE_DEVICE while sacrificing CONFIG_ZONE_DMA. > >> Distributions like Ubuntu has started enabling CONFIG_ZONE_DEVICE and > >> thus breaking parallel port. Please have a look at > >> https://bugzilla.kernel.org/show_bug.cgi?id=110931 for the bug report. > >> > >> Apart from parallel port I can see some sound drivers will also break. > >> > >> Now what is the possible solution for this? > > > > The tradeoff here is enabling direct-I/O for persistent memory vs > > support for legacy devices. > > > > One possible solution is to alias ZONE_DMA and ZONE_DEVICE. At early > > boot if pmem is detected disable these legacy devices, or the reverse > > disable DMA to persistent memory if a legacy device is detected. The > > latter is a bit harder to do as I think we would want to make the > > decision early during memory init before we would know if any parallel > > ports or ISA sound cards are present. > > ...another option that might be cleaner is to teach GFP_DMA to get > memory from a different mechanism. I.e. don't use the mm-zone > infrastructure to organize that small 16MB pool of memory. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
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