Commit Graph

7 Commits

Author SHA1 Message Date
David Malone
b0f4bb511e Make the MTRR code a bit more defensive - this should help people
trying to run X on some Athlon systems where the BIOS does odd things
(mines an ASUS A7A266, but it seems to also help on other systems).

Here's a description of the problem and my fix:

        The problem with the old MTRR code is that it only expects
        to find documented values in the bytes of MTRR registers.
        To convert the MTRR byte into a FreeBSD "Memory Range Type"
        (mrt) it uses the byte value and looks it up in an array.
        If the value is not in range then the mrt value ends up
        containing random junk.

        This isn't an immediate problem. The mrt value is only used
        later when rewriting the MTRR registers. When we finally
        go to write a value back again, the function i686_mtrrtype()
        searches for the junk value and returns -1 when it fails
        to find it. This is converted to a byte (0xff) and written
        back to the register, causing a GPF as 0xff is an illegal
        value for a MTRR byte.

	To work around this problem I've added a new mrt flag
	MDF_UNKNOWN.  We set this when we read a MTRR byte which
	we do not understand.  If we try to convert a MDF_UNKNOWN
	back into a MTRR value, then the new function, i686_mrt2mtrr,
	just returns the old value of the MTRR byte. This leaves
	the memory range type unchanged.

I have seen one side effect of the fix, which is that ACPI calls
after X has been run seem to hang my machine. As running X would
previously panic the machine, this is still an improvement ;-)

I'd like to MFC this before the 4.6 code freeze - please let me
know if it causes any problems.

PR:		28418, 25958
Tested by:	jkh, Christopher Masto <chris@netmonger.net>
MFC after:	2 weeks
2002-04-14 20:19:13 +00:00
Dima Dorfman
7309915e7a Nuke unused variables. 2001-06-24 23:41:57 +00:00
David E. O'Brien
1a37aa566b Add `_PATH_DEVZERO'.
Use _PATH_* where where possible.
2000-12-09 09:35:55 +00:00
Brian Feldman
2e61f987ad Make memcontrol(8) able to delete the segments starting at a base of 0
which it can create..
2000-03-20 22:53:32 +00:00
Peter Wemm
97d92980a9 $Id$ -> $FreeBSD$ 1999-08-28 01:35:59 +00:00
Mike Smith
5fd6b620bb Make memcontrol's internal help actually work. No substitute for a real
manpage, but at least now you can get syntax help without resorting
to reading the source.
1999-07-20 04:33:14 +00:00
Mike Smith
53f17f08ba Commandline tool for manipulating memory range attributes. 1999-04-07 04:11:14 +00:00