From: Gleb Natapov <gleb@redhat.com>
To: Jim MacArthur <jim@mode7.co.uk>
Cc: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org
Subject: Re: Starting a VM using /dev/kvm
Date: Thu, 21 Nov 2013 09:27:19 +0200 [thread overview]
Message-ID: <20131121072719.GF2108@redhat.com> (raw)
In-Reply-To: <CAMGYSmEpA3LruqoVrXH06m3h2pGrqooGPdQACTkCFVB8yj3hgQ@mail.gmail.com>
On Thu, Nov 21, 2013 at 12:39:49AM +0000, Jim MacArthur wrote:
> On 20 November 2013 17:28, Paolo Bonzini <pbonzini@redhat.com> wrote:
> > Il 20/11/2013 00:56, Jim MacArthur ha scritto:
> >> The question is, how does a new vcpu start up? Will it start in full
> >> 64-bit mode or 16-bit real mode?
> >
> > By default it start in 16-bit real mode, with CS=0xf000 and EIP=0xfff0,
> > but CS.base = 0xffff0000. However, you can send ioctls to modify
> > CR0/CR4/EFER and place the VCPU in whatever mode you'd like to have.
>
> After reading this I added a call to KVM_GET_SREGS. Everything you say
> here matches my experience except that CS.base=0xf0000.
> So I adjusted my memory to cover physical address 0xFFFF0, and now
> it's happily running instructions (NOPs, at least.)
> I'm a bit puzzled that it didn't start with CS.base=0xffff0000, but it
> doesn't matter, I've done what I wanted to do for now.
>
What is your kernel version?
--
Gleb.
next prev parent reply other threads:[~2013-11-21 7:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-19 23:56 Starting a VM using /dev/kvm Jim MacArthur
2013-11-20 17:28 ` Paolo Bonzini
2013-11-21 0:39 ` Jim MacArthur
2013-11-21 7:27 ` Gleb Natapov [this message]
2013-11-21 23:57 ` Jim MacArthur
2013-11-22 6:56 ` Gleb Natapov
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