linux-kernel - Re: [PATCH] KVM: Add wrapper script around QEMU to test kernels

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Message-ID: <4EB94340.5040205@redhat.com>
Date:	Tue, 08 Nov 2011 16:57:04 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
CC:	Alexander Graf <agraf@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org list" <kvm@...r.kernel.org>,
	qemu-devel Developers <qemu-devel@...gnu.org>,
	Pekka Enberg <penberg@...nel.org>,
	Am?rico Wang <xiyou.wangcong@...il.com>,
	Blue Swirl <blauwirbel@...il.com>
Subject: Re: [PATCH] KVM: Add wrapper script around QEMU to test kernels

On 11/08/2011 04:52 PM, Christoph Hellwig wrote:
> On Tue, Nov 08, 2011 at 04:41:40PM +0200, Avi Kivity wrote:
> > On 11/06/2011 03:35 AM, Alexander Graf wrote:
> > > To quickly get going, just execute the following as user:
> > >
> > >     $ ./Documentation/run-qemu.sh -r / -a init=/bin/bash
> > >
> > > This will drop you into a shell on your rootfs.
> > >
> > 
> > Doesn't work on Fedora 15.  F15's qemu-kvm doesn't have -machine or
> > -virtfs.  Even qemu.git on F15 won't build virtfs since xattr.h
> > detection is broken (patch posted).
>
> Nevermind that running virtfs as a rootfs is a really dumb idea.  You
> do now want to run a VM that has a rootfs that gets changed all the
> time behind your back.

True.

> Running qemu -snapshot on the actual root block device is the only
> safe way to reuse the host installation, although it gets a bit
> complicated if people have multiple devices mounted into the namespace.

How is -snapshot any different?  If the host writes a block after the
guest has been launched, but before that block was cowed, then the guest
will see the new block.

It could work with a btrfs snapshot, but not everyone uses that.

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

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