linux-kernel - Re: [Qemu-devel] [RFC] Next gen kvm api

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Message-ID: <4F3BB59D.2020505@redhat.com>
Date:	Wed, 15 Feb 2012 15:39:41 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Rusty Russell <rusty@...abs.org>
CC:	Anthony Liguori <anthony@...emonkey.ws>,
	Gleb Natapov <gleb@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>
Subject: Re: [Qemu-devel] [RFC] Next gen kvm api

On 02/07/2012 08:12 PM, Rusty Russell wrote:
> > I would really love to have this, but the problem is that we'd need a
> > general purpose bytecode VM with binding to some kernel APIs.  The
> > bytecode VM, if made general enough to host more complicated devices,
> > would likely be much larger than the actual code we have in the kernel now.
>
> We have the ability to upload bytecode into the kernel already.  It's in
> a great bytecode interpreted by the CPU itself.

Unfortunately it's inflexible (has to come with the kernel) and open to
security vulnerabilities.

> If every user were emulating different machines, LPF this would make
> sense.  Are they?  

They aren't.

> Or should we write those helpers once, in C, and
> provide that for them.

There are many of them: PIT/PIC/IOAPIC/MSIX tables/HPET/kvmclock/Hyper-V
stuff/vhost-net/DMA remapping/IO remapping (just for x86), and some of
them are quite complicated.  However implementing them in bytecode
amounts to exposing a stable kernel ABI, since they use such a vast
range of kernel services.

-- 
error compiling committee.c: too many arguments to function

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