Re: [hackers-il] Xen
- On Sat, Oct 22, 2005 at 12:23:46PM -0700, Omer Shapira wrote:
> A layman's question - what is the easiest way forWhich beast? Linux or Xen?
> someone who doesn't remember much of a linux kernel
> (me) to start tweaking the beast?
> In addition, I am very interested on how modernI'm not quite sure I'm following, but in general there are three ways
> compilers can cope with virtualized CPUs.
> I assume that cpu calls caused by virtualized
> resources can get the CPU frontend insane quite fast.
> Correct me if I am wrong.
of virtualizing code if your CPU doesn't support it:
- rewrite the priviledged bits at run time (VMWare's dynamic rewriting
of executing code before it executes)
- rewrite the priviledged bits at your leisure, then recompile (Xen's
- have your toolchain rewrite the priviledged bits when you compile
the code (L4 group's afterburner project - see
All of these approaches concentrate on running non-priviledged code
natively (unlike CPU emulators like Bochs and QEMU, which translate
and emulate all instructions) and only deal with priviledged
Does this answer the question?
> In addition, I am intrigued by a problem of providingAh, now that's a question I am wont to discuss at length for multiple
> networking hardware/software necessary for efficient
> virutalization of network devices.
hours at a time, and have been known to do so :-)
> Consider, for example, a switch chip (anIf you're at a situation where you are likely to have lots of
> uber-super-hyper NIC) that does TCP session handshake
> offloading, and interrupts only on sessions that are
> not to be bridged, but are intended for the device
> itself. Either the silicon intended for the port
> buckets is multiplied (expensive, dollar-wise), or
> lots of interrupts are delivered to the CPU
> (expensive, cycle-wise).
interrupts delivered, you'd probably switch to chip to polling mode
(a-la NAPI in Linux).
Here's a question for discussion: does virtualization support *in
devices* make sense? or should we stick with "regular devices" and let
the software multiplex it?
> I admit these questions have little with ethics ofWe now return you to your regularly scheduled shlomifogram!
> software licensing as opposed to licencing of software
> ethics, and are rather (paraphrasing nyh) examples fo
> "engineering mumbo-jumbo", but these questions bug me
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