Date: Thu, 02 Feb 2006 15:33:20 -0700 From: Scott Long <scottl@samsco.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: freebsd-current@www.freebsd.org Subject: Re: mapping "random" physical memory into kernel Message-ID: <43E288B0.6080804@samsco.org> In-Reply-To: <17378.34270.630897.473143@grasshopper.cs.duke.edu> References: <17378.34270.630897.473143@grasshopper.cs.duke.edu>
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Andrew Gallatin wrote: > Can somebody please remind me what the supported way to establish a > kernel virtual address for a "random" chunk of physical memory is? > I'm currently using pmap_mapdev() directly, but that just feels > dirty... > > I need to twiddle the settings of an Nvidia NF4 bridge in extended > PCI config space (offset 0x178). These offsets are not accessible > via normal pci config space writes, but are doable when you use the > 0xe000000 mapping. Extended pci config space is supported by default on i386, but I haven't gotten around to figuring out the right strategy for amd64. I'd like to be able to map the entire 256MB range instead of the on-demand approach with i386, but I need to learn more about the various VM maps on amd64 first. > > The problem is that this memory is not really associated with > anything, so a normal bus_alloc_resource() allocation doesn't > seem like it would work. pmap_mapdev is the correct interface for this. Scott
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