From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040614 Firefox/0.8 Description of problem: A `cat /proc/mtrr` displays "strange" looking values for the size on Intel based x86_64 (EM64T plattform) systems. It looks like that the displayed size is 16 times bigger than the real size of that memory region. Version-Release number of selected component (if applicable): 2.4.21-17.EL How reproducible: Always Steps to Reproduce: 1. Install Red Hat EL 3 Upd. 3 beta on Intel based x86_64 system 2. Login as root 3. cat /proc/mtrr Actual Results: Here an example of the x86_64 version of RHEL 3: [root@localhost root]# uname -a Linux localhost.localdomain 2.4.21-17.EL #1 SMP Thu Jul 8 19:34:05 EDT 2004 x86_64 x86_64 x86_64 GNU/Linux [root@localhost root]# cat /proc/mtrr reg00: base=0x00000000 ( 0MB), size=8192MB: write-back, count=1 reg01: base=0x1ff00000 ( 511MB), size= 16MB: uncachable, count=1 [root@localhost root]# Note that the machine is only eqipped with 512 MB of RAM. Expected Results: Same as above, but this time the 32-bit Version of RHEL 3 Upd. 2: [root@localhost root]# uname -a Linux localhost.localdomain 2.4.21-15.ELsmp #1 SMP Thu Apr 22 00:18:24 EDT 2004 i686 i686 i386 GNU/Linux [root@localhost root]# cat /proc/mtrr reg00: base=0x00000000 ( 0MB), size= 512MB: write-back, count=1 reg01: base=0x1ff00000 ( 511MB), size= 1MB: uncachable, count=1 reg02: base=0xf0000000 (3840MB), size= 16MB: write-combining, count=1 [root@localhost root]# Identical hardware, here 512 MB size is displayed as expected. Additional info: Looks like this bug is only occuring on Intel based systems. I've seen it on a Prescott (examples above) but also on a Dual Xeon workstation. A dual opteron workstation seems not to be affected by this. On the same hardware the 2.6.5 kernel of SuSE distribution shows no error in the size. I just want to report this as a minor bug, impacts on other things (like 3D graphics) are not observed so far. But we just made a few minor tests.
Reassigning to lwoodman as he looked at it and came up with the fix.
*** This bug has been marked as a duplicate of 137201 ***
A fix for this problem has just been committed to the RHEL3 U5 patch pool this evening (in kernel version 2.4.21-27.16.EL).
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2005-294.html