[Xen-devel] Re: [PATCH] xen: core dom0 support

[Ingo Molnar <mingo@xxxxxxx>]

* H. Peter Anvin <hpa@xxxxxxxxx> wrote:

> Ingo Molnar wrote:
> > 
> > Associativity effects do depend on the kernel image layout 
> > and on the precise allocations of kernel data structure 
> > allocations we do during bootup - and they dont really 
> > change after that.
> > 
> 
> By the way, there is a really easy way (if a bit time 
> consuming) to get the actual variability here -- you have to 
> reboot between runs, even for the same kernel.  It makes the 
> data collection take a long time, but at least it can be 
> scripted.

Since it's the same kernel image i think the only truly reliable 
method would be to reboot between _different_ kernel images: 
same instructions but randomly re-align variables both in terms 
of absolute address and in terms of relative position to each 
other. Plus randomize bootmem allocs and never-gets-freed-really 
boot-time allocations.

Really hard to do i think ...

        Ingo

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