Date: Fri, 30 Jul 2010 01:09:18 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: pebu3op@googlemail.com Cc: freebsd-hackers@freebsd.org, Sergey Babkin <babkin@verizon.net> Subject: Re: coherence-problem on the mapped memory buffer Message-ID: <4C51FC0E.9050204@icyb.net.ua> In-Reply-To: <201007292341.21123.pebu3op@googlemail.com> References: <382607918.1356296.1280433776963.JavaMail.root@vms170009.mailsrvcs.net> <4C51E198.8060800@icyb.net.ua> <201007292341.21123.pebu3op@googlemail.com>
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on 30/07/2010 00:41 Alexander Fiveg said the following: > Thanks a lot for your answers. But i am afraid i do not have enough > experience to solve these tasks. Could you please provide me with helpful > information how to: > - get access to the pages associated with a certain memory-buffer ? > I mean, I want to get the structures, that describe the page properties I > should change (for instance, in order to make the page non-cacheable). > > if you are aware of any good papers or examples in the system code, where > these topics are covered, I would appreciate it if you gave me the > references. I don't have a recipe, but some pointers to get you started: 1. investigate BUS_DMA_NOCACHE, see bus_dma(9) 2. check sys/dev/sound/pci/hda/hdac.c for HDAC_F_DMA_NOCACHE and comment about PCIe snoop - this might be relevenat 3. see pmap_change_attr for way to change caching type for a memory mapping 4. hope that more knowledgeable people (experts) provide their advice, keep nudging them via mailing list(s) :-) -- Andriy Gapon
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