Archive for the ‘xen’ Tag

Why does Intel’s Processors still suck

I am no fan of AMD, VIA or any other processor manufacturer. I use AMD at home and Intel at work. And in my experience AMD’s processors may have lost to reborn netburst architecture based Intel processors, they still are technically good for *me*.Why?

Here is the rant. Intel makes some really shitty processors as far as virtualisation is concerned(read VT technology in Intel lingo). Intel’s architecture allows only protected mode instructions to be virtualized and not the real mode instructions. This may sound like – “Okay, who cares about real mode instructions anymore? We all are using 32/64 bit protected instructions these days”. Thats right, but thanks to IBM and brethren we still have to rely on real mode instructions while booting initially. Many bootloaders which use some real mode instructions will not be able to do anything under guest virtual machines booting under a VMM.(e.g while installing a HVM Guest under XEN) The intial part of the setup to switch to a protected mode is done with the help of some real mode instructions and thus cannot complete resulting is a blank screen or an endless wait. Example :- You cannot install a guest from a standard Linux ISO, if the loader on ISO uses real mode instructions(BTW isolinux does use some AFAIR).

Fret not, there is a solution. Emulate, yes emulate every real mode instruction rather than virtualize under intel architecture. Sounds like suckage, yes it does. So somethings may work  and some may not depending on whether the instruction has been emulated or not.

FWIW, AMD has a better and clear virtualization capability, all instructions can be virtualized irrespective of the real/protected/legacy mode.

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