RE: [Xen-users] FIXED!!! amd64 system only seeing 3.5gb instead of 4gb of memory

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

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Rafal Kupka
> Sent: 18 June 2007 12:34
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] FIXED!!! amd64 system only seeing 
> 3.5gb instead of 4gb of memory
> 
> On Mon, Jun 18, 2007 at 11:35:56AM +0200, Petersson, Mats wrote:
> Hello,
> 
> > > The fix makes me think that the bug is a bit 
> heisenbug-ish... but it
> > > works for me.
> > 
> > Yes, it looks like a "compiler issue" that is fixed by forcing the
> > compiler to not optimize the variable by using volatile - 
> not the ideal
> > solution, but I guess fixing the compiler may be even more 
> difficult.
> > [Not knowing what the code looks like - but I suppose the "cont"
> > variable isn't updated by an interrupt or external hardware!]
> 
> I thought the same, but one grub stage2 file behaves differently on
> two motherboards. It fails to detect[1] e820 memory map on my 
> computer,
> but copied to friend's one works perfectly. I think if it's
> compiler bug[2] that copy shouldn't work on both computers.

Well, the link in the original post says that the "while-loop is completely 
removed", which I took to mean that the author of the bugfix had actually 
examined the code generated by the compiler. 

Obviously, copying files from one machine to another shouldn't change the 
behaviour of the code if "copy" works right (if in doubt, do "md5sum some-file" 
to check that the content of the file hasn't changed). 

Unfortunately, just because one bug is fixed, doesn't mean that others aren't 
still in there. 

--
Mats
> 
> Regerds,
> Kupson
> [1] displaymem command doesn't work
> [2] optimize loop or function call to nothing or something similar
> 
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