Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33

Avi Kivity
2009-12-23T21:02:25Z

On 12/23/2009 10:36 PM, Avi Kivity wrote:
> On 12/23/2009 06:44 PM, Gregory Haskins wrote:
>>
>>> - Are a pure software concept
>> By design. In fact, I would describe it as "software to software
>> optimized" as opposed to trying to shoehorn into something that was
>> designed as a software-to-hardware interface (and therefore has
>> assumptions about the constraints in that environment that are not
>> applicable in software-only).
>>
>
> And that's the biggest mistake you can make. Look at Xen, for
> instance. The paravirtualized the fork out of everything that moved
> in order to get x86 virt going. And where are they now? x86_64
> syscalls are slow since they have to trap to the hypervisor and
> (partially) flush the tlb. With npt or ept capable hosts performance
> is better for many workloads on fullvirt. And paravirt doesn't
> support Windows. Their unsung hero Jeremy is still trying to upstream
> dom0 Xen support. And they get to support it forever.
>
> VMware stuck with the hardware defined interfaces. Sure they had to
> implement binary translation to get there, but as a result, they only
> have to support one interface, all guests support it, and they can
> drop it on newer hosts where it doesn't give them anything.

As a twist on this, the VMware paravirt driver interface is so
hardware-like that they're getting hardware vendors to supply cards that
implement it. Try that with a pure software approach.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.