Date: Tue, 15 Nov 2005 10:30:57 -0500 From: John Baldwin <jhb@freebsd.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: freebsd-current@freebsd.org Subject: Re: NVidia driver for amd64 / Page Attribute Table status? Message-ID: <200511151030.58879.jhb@freebsd.org> In-Reply-To: <17273.59797.727269.288021@grasshopper.cs.duke.edu> References: <436E66FB.60700@desk.pl> <200511141153.27640.jhb@freebsd.org> <17273.59797.727269.288021@grasshopper.cs.duke.edu>
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On Tuesday 15 November 2005 08:58 am, Andrew Gallatin wrote: > John Baldwin writes: > > On Sunday 13 November 2005 06:20 am, Marcin Koziej wrote: > > > Would it be possible for You to put a snapshot patch against CURRENT > > > for jhb_pat branch somewhere? I can't make it with P4DB interface, and > > > i don't have access to p4. > > > > > > Best regards, > > > m. > > > > Sure, though it's not commit ready yet. > > > > http://www.FreeBSD.org/~jhb/patches/pat.patch > > I have a question about this.. I maintain a driver where our > device really, really wants to have its memory mapped write-combined. > I currently use mem_range_attr_set() to (try to) do this. > > The problem is that some BIOSes leave useless uncacheable MTRR > attributes laying around which obscure our device (and in fact, nearly > all the PCI memory space). In order for the mem_range_attr_set() to > work, there cannot be another conflicting MTRR attribute already > covering our memory, so we play games with shell scripts which try to > remove the uncacheable attributes. This is a royal PITA. > > With your new PAT stuff, does this mean that I'll no longer have > to worry about the MTRR attributes, and I can be certain of getting > my memory mapped write-combined? On modern CPUs, yes. (Anything later than a PIII I think). You'll just be able to use pmap_mapdev_attr(), though it will only work on i386 and eventually amd64 for now. Also, that currently only affects the in-kernel mapping, there currently isn't anything to handle the cache mode of user mappings. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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