RE: [Xen-devel] KernelBUGatarch/x86_64/mm/../../i386/mm/hypervisor.c:197

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Christophe Saout
> Sent: 05 October 2006 15:19
> To: Ian Pratt
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] 
> KernelBUGatarch/x86_64/mm/../../i386/mm/hypervisor.c:197
> 
> Am Donnerstag, den 05.10.2006, 05:02 +0100 schrieb Ian Pratt:
> 
> > Glad it works for you, but I wish we understood what was 
> going on a bit
> > more. It may be that the bios is just borked and the e820 
> map it gives
> > xen misses some regions that it steals for other purposes. 
> It would be
> > pretty surprising if Xen had bugs in its e820 code. 
> > 
> > It might be interesting to post the xm dmesg output with the two
> > different BIOS settings to see if there's anything unusual about the
> > e820 map.
> 
> The only difference is in the Physical RAM map:
> 
> Broken (with memory hole remapping turned on):
> 
> (XEN) Physical RAM map:
> (XEN)  0000000000000000 - 000000000009fc00 (usable)
> (XEN)  000000000009fc00 - 00000000000a0000 (reserved)
> (XEN)  00000000000e8000 - 0000000000100000 (reserved)
> (XEN)  0000000000100000 - 00000000bfff0000 (usable)
> (XEN)  00000000bfff0000 - 00000000bffff000 (ACPI data)
> (XEN)  00000000bffff000 - 00000000c0000000 (ACPI NVS)
There is a HOLE here - c0000000 to ff780000 is "missing". That's 1GB
minus a little bit. 
> (XEN)  00000000ff780000 - 0000000100000000 (reserved)
> (XEN)  0000000100000000 - 000000030e000000 (usable)
> (XEN) System RAM: 11487MB (11763260kB)
> 
> Working (with memory hole remapping turned off):
> 
> (XEN) Physical RAM map:
> (XEN)  0000000000000000 - 000000000009fc00 (usable)
> (XEN)  000000000009fc00 - 00000000000a0000 (reserved)
> (XEN)  00000000000e8000 - 0000000000100000 (reserved)
> (XEN)  0000000000100000 - 00000000efff0000 (usable)
This area is bigger, which probably explains the more usable memory. 
> (XEN)  00000000efff0000 - 00000000effff000 (ACPI data)
> (XEN)  00000000effff000 - 00000000f0000000 (ACPI NVS)
The hole here is much smaller... Only f0000000 - ff780000, around 256MB
if my mental arithmetic isn't playing up (which it does quite
frequently). 
> (XEN)  00000000ff780000 - 0000000100000000 (reserved)
> (XEN)  0000000100000000 - 0000000300000000 (usable)
> (XEN) System RAM: 12031MB (12320316kB)
> 
> The strange thing is that the upper configuration shows even 
> less memory
> that the second one which has only 256MB missing?

That may be explained by the above comments - but I can't explain what's
going wrong in Xen with this... 

--
Mats
> 
> >  Might be worth comparing against what Linux prints too.
> 
> Ok, I'll try to boot the Dom0 without hypervisor to get some numbers
> from native Linux for comparison.
> 
> As Keir suggested, this really might be a BIOS bug. Our 
> hardware vendor
> has notified the motherboard manufacturer to have this checked (this
> already was the latest version).
> 
> 
> 
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> 
> 
> 



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