[Xen-devel] Re: [GIT PULL] xen /proc/mtrr implementation

[Ingo Molnar <mingo@xxxxxxx>]

* Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:

> It's not really virtualized.  We're talking about dom0, which is 
> the guest domain which has access to the real machine's real 
> hardware; the MTRR is part of that.

That is a really broken model and design of virtualization: 
splitting the hypervisor into Xen and then a separate Linux dom0 
entity because reality called home a few years ago and you needed 
actual working drivers and hardware support and a developer 
community to pull that off ...

Here Xen invades an already fragile piece of upstream code 
(/proc/mtrr) that is obsolete and on the way out. If you want a 
solution you should add PAT support to Xen and you should use recent 
upstream kernels. Or you should emulate /proc/mtrr in _Xen the 
hypervisor_, if you really care that much - without increasing the 
amount of crap in Linux.

Without a better reason than what you've given so far the answer is 
really: "no thanks" ...

My suspicion is that Linus would (rightfully) refuse to pull such a 
broken approach from me, so why should i pull it? If i'm wrong and 
if you can get an Acked-by from Linus _before_ sending a pull 
request we can override my NAK. I've Cc:-ed him, in case he wants to 
express an opinion.

        Ingo

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