Bug 58867 – Adding mem=128M requires uppermem to be set as 127M

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Bug 58867 - Adding mem=128M requires uppermem to be set as 127M

Summary:	Adding mem=128M requires uppermem to be set as 127M

Status:	CLOSED RAWHIDE

Aliases:	None

Product:	Red Hat Linux
Classification:	Retired
Component:	grub (Show other bugs)
Sub Component:
Version:	7.2
Hardware:	i386 Linux

Priority	medium Severity high
Target Milestone:	---
Target Release:	---
Assigned To:	Jeremy Katz
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Reported:	2002-01-25 22:00 EST by Yusuf Goolamabbas
Modified:	2008-05-01 11:38 EDT (History)
CC List:	0 users

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Doc Type:	Bug Fix
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Last Closed:	2002-01-25 22:00:32 EST
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Description Yusuf Goolamabbas 2002-01-25 22:00:27 EST

From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.7+) Gecko/20020123

Description of problem:
If one wants to boot a system with mem=128M and an initrd exists
it requires that uppermem be set as
uppermem 130048
instead of 
uppermem 130172


Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Modify /etc/grub.conf to add mem=128M to the kernel line
2. Add an uppermem 130172 before the kernel command line
3. Reboot


Actual Results:  Boot fails with grub complaining that it can't find the root device
Taking out the mem=128M and uppermem command makes it work
Another way is to modify uppermem to be
uppermem 130048

This is mentioned in this URL though I can't figure out why
http://www.uwsg.iu.edu/hypermail/linux/kernel/0005.3/1201.html

I don't know if this is a grub feature/bug or maybe some grub/kernel interaction

Is there a formulae to determine the correct value of uppermem depending on the
value of mem="XX"M. If so, could this be documented somewhere


Additional info:

Comment 1 Jeremy Katz 2002-01-25 22:28:13 EST

Actually as of the package I just built (grub-0.91-2), you shouldn't have to
specify uppermem anymore as it will parse the kernel command line and figure out
where the initrd is supposed to be loaded.

Comment 2 Yusuf Goolamabbas 2002-01-25 22:32:43 EST

Is this being slated for an errata release ?

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