Bug 504645 - kernel-xen fails to detect the full amount of RAM on a Dell PE1950 (E5420) system
kernel-xen fails to detect the full amount of RAM on a Dell PE1950 (E5420) sy...
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: kernel-xen (Show other bugs)
x86_64 Linux
low Severity urgent
: rc
: ---
Assigned To: Xen Maintainance List
Red Hat Kernel QE team
Depends On:
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Reported: 2009-06-08 12:23 EDT by George B. Magklaras
Modified: 2009-06-08 13:43 EDT (History)
2 users (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2009-06-08 13:43:33 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description George B. Magklaras 2009-06-08 12:23:09 EDT
Description of problem:
Dell PowerEdge 1950 fully RHN patched (firmware + software) fails to recognize the full amount of installed RAM when booted with the latest xen-kernel. The problem does not occur with non xen kernels, where the full amount of RAM memory is detected properly.

Version-Release number of selected component (if applicable):
Red Hat Enterprise Linux Server release 5.3 (Tikanga)
kernel-xen.x86_64                         2.6.18-128.1.10.el5
grub.x86_64                               0.97-13.2   (in case grub is to blame)

How reproducible:
Highly reproducible on all Dell PowerEdge 1950 (E5420) boxes 

Steps to Reproduce:
1. Hardware test and fully RHN update a Dell PE1950 (E5420) system which includes virtualization entitlement
2. Boot the system into the non-xen enabled kernel. Observe the output of 'free'.
3. Boot the system into the xen-kernel. Observe the output of free.
4. Repeats steps 2-3 at least twice to make sure the failure is consistent.
Actual results:
[root@cnkeeper ~]# free
             total       used       free     shared    buffers     cached
Mem:      33554432    1068904   32485528          0      18264     164664
-/+ buffers/cache:     885976   32668456
Swap:     32767992          0   32767992

Expected results:
[root@cnkeeper ~]# free
             total       used       free     shared    buffers     cached
Mem:      64971128     432788   64538340          0      27500     289052
-/+ buffers/cache:     116236   64854892
Swap:     32767992          0   32767992

(as reported by the non-xen kernel

Additional info:
i)A similar incident report on FC9 can be found on id 250299

ii)Snapshot of dmidecode of the PE 1950 (E5420) system:
BIOS Information
        Vendor: Dell Inc.
        Version: 2.5.0
        Release Date: 09/12/2008
        Address: 0xF0000
        Runtime Size: 64 kB
        ROM Size: 1024 kB
                ISA is supported
                PCI is supported
                PNP is supported
                BIOS is upgradeable
                BIOS shadowing is allowed
                ESCD support is available
                Boot from CD is supported
                Selectable boot is supported
                EDD is supported
                Japanese floppy for Toshiba 1.2 MB is supported (int 13h)
                5.25"/360 KB floppy services are supported (int 13h)
                5.25"/1.2 MB floppy services are supported (int 13h)
                3.5"/720 KB floppy services are supported (int 13h)
                Print screen service is supported (int 5h)
                8042 keyboard services are supported (int 9h)
                Serial services are supported (int 14h)
                Printer services are supported (int 17h)
                CGA/mono video services are supported (int 10h)
                ACPI is supported
                USB legacy is supported
                BIOS boot specification is supported
                Function key-initiated network boot is supported
                Targeted content distribution is supported
        BIOS Revision: 2.5
Comment 1 Rik van Riel 2009-06-08 13:43:33 EDT
The dom0 kernel is limited to 32GB by default, but the full amount of memory is still available for guests.  This is done to limit the overhead of managing that much memory in dom0 - after all, if people install kernel-xen, they will do so in order to run guests.

Type 'xm info' or look at the virt-manager graphical interface to see all of system memory.

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