[Xen-devel] difference between xen hypervisor and common kernel on handling BIOS's e820 map ?

[Lin-bao Zhang <zhang.linbao@xxxxxxxxx>]

in a same , I have xen-kernel and common kernel installed ,
in grub.conf , just like this:

title Red Hat Enterprise Linux Server (2.6.18-268.el5xen)
root (hd0,0)
kernel /boot/xen.gz-2.6.18-268.el5  loglvl=all guest_loglvl=all sync_console 
console_to_ring com1=115200,8n1 console=com1
module /boot/vmlinuz-2.6.18-268.el5xen ro root=LABEL=/1 console=hvc0 
earlyprintk=xen nomodeset
module /boot/initrd-2.6.18-268.el5xen.img

title Red Hat Enterprise Linux Server (2.6.18-268.el5)
        root (hd0,0)
        kernel /boot/vmlinuz-2.6.18-268.el5 ro root=LABEL=/1 console=tty0 
console=ttyS0,115200
        initrd /boot/initrd-2.6.18-268.el5.img

--------------
but I found difference about e820map from the two kernels :

common kernel: --------------------------------
BIOS-provided physical RAM map:
 BIOS-e820: 0000000000010000 - 0000000000090400 (usable)
 BIOS-e820: 0000000000090400 - 0000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 000000007f5f0000 (usable)
 BIOS-e820: 000000007f5f0000 - 000000007f62c000 (ACPI data)
 BIOS-e820: 000000007f62c000 - 000000007f62d000 (usable)
 BIOS-e82: 000000007f62d000 - 00000000779d000 (reserved)
 BIOS-e820: 0000000779d000 - 000000007f7a0000 (ACPI data)
 BIOS-e0: 00000007f7a0000 - 0000000090000000 (reserved)
 BIOS-e820: 00000000fec00000 - 00000000fee10000 (reserved)
 BIOS-e820: 00000000ff800000 - 0000000100000000 (eservd)
 BIOS-e820: 0000000100000000 -0000000480000000 (usable)
 BIOS-e820: 0000002000000000 - 0000002400000000 (usable)
 BIOS-e820: 0000004000000000 - 0000004400000000 (usable)
 BIOS-e820: 0000006000000000 - 00000600000000 (usable)

xen-kernel:
 Xen-e820 RAM map:
(XEN)  0000000000000000 - 0000000000090400 (usable)
(XEN)  0000000000090400 - 00000000000a0000 (reserved)
(XEN)  00000000000f0000 - 0000000000100000 (reserved)
(XEN)  0000000000100000 - 000000007f5f0000 (usable)
(XEN)  000000007f5f0000 - 000000007f62c000 (ACPI data)
(XEN)  000000007f62c000 - 000000007f62d000 (usable)
(XEN)  000000007f62d000 - 000000007f79d000 (reserved)
(XEN)  000000007f79d000 - 000000007f7a0000 (ACPI data)
(XEN)  000000007f7a0000 - 0000000090000000 (reserved)
(XEN)  00000000fec00000 - 00000000fee10000 (reserved)
(XEN)  00000000ff800000 - 0000000100000000 (reserved)
(XEN)  0000000100000000 - 0000000480000000 (usable)
(XEN)  0000002000000000 - 0000002400000000 (usable)
(XEN)  0000004000000000 - 0000004400000000 (usable)
(XEN)  0000006000000000 - 0000006400000000 (usable)      
(XEN) System RAM: 65525MB (67098116kB)

I diff them in a picture :


as my existing knowledge , e820 map information is provided by BIOS ,it should 
be same for all OS(windows and linux) , OS just use it . 
but why xen-kernel's e820 map is different from that of common-kernel.

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