Re: [Xen-devel] question about the guestOS boot

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> There is a difference in Xen-linux start and a regular linux start, and
> that is that Xen-linux starts in 32-bit protected mode (but Paging is not
> yet enabled), whereas the regular Linux starts with real-mode (16-bit
> mode), and does a few instructions before it gets into 32-bit mode.

AFAIK paging is enabled for a Xen paravirtualised guest; there is a set of 
bootstrap pagetables put in place by the domain builder, which map enough 
memory to get the domain started.

Cheers,
Mark

> > then I do not know where does the guestOS start with in the code
> > could you told me where or which function does the guestOS
> > start with ?
>
> As above. The actual code that the Xen kernel starts at is in
> .../linux-<ver>-xen/arch/<mach>/kernel/head-xen.S
>
> --
> Mats
>
> > Thanks in advance
> >
> > Petersson, Mats 写道:
> > >> -----Original Message-----
> > >> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> > >> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of tgh
> > >> Sent: 09 March 2007 08:17
> > >> To: xen-devel
> > >> Subject: [Xen-devel] question about the guestOS boot
> > >>
> > >> hi
> > >> I try to understand the code about vm create
> > >> and now I am confused about which code does the guestOS start
> > >> with to run ?
> > >>
> > >> xen domain0 uses the function xc_domain_creat() and
> > >> xc_linux_build() to
> > >> prepare the necessary struct such as vcpu_guest_context and
> > >> other things
> > >> for vm guestOS to bootup , in the xc_linux_build(),the
> >
> > initrd is also
> >
> > >> loaded in,is it right?
> > >> then guestOS does not run the regular bootloader ,is it right?
> > >
> > > That is correct.
> > >
> > >> then I am confused about which function or which lines of the
> > >> code does
> > >> the guestOS start with ?
> > >
> > > Can you explain your confusion a bit more - I'm not
> >
> > entirely sure what
> >
> > > you're asking, and it's very hard to answer questions when you don't
> > > know the actual question.
> > >
> > > Also, it's much better if you explain a little bit about what you're
> > > trying to achieve (I've previously used the example of
> >
> > someone having a
> >
> > > puncture, going to ask the mechanic how to loosen a wheel-nut, then
> > > going to ask how to jack up the car, then asking how to tighten the
> > > wheel-nut, when the actual problem is a punctured tyre, and
> >
> > the "right"
> >
> > > question to ask a mechanic is "How do I replace my
> >
> > punctured tyre with
> >
> > > the spare wheel?").
> > >
> > > Asking the overall question you're trying to solve will
> >
> > give you a more
> >
> > > complete answer to what you're trying to do, rather than a detailed
> > > answer on the point where you're at (and that may actually
> >
> > not help your
> >
> > > overall problem at all).
> > >
> > > --
> > > Mats
> > >
> > >> could you help me
> > >>
> > >> Thanks in advance
> > >>
> > >>
> > >> _______________________________________________
> > >> Xen-devel mailing list
> > >> Xen-devel@xxxxxxxxxxxxxxxxxxx
> > >> http://lists.xensource.com/xen-devel
> > >
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > > http://lists.xensource.com/xen-devel
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
>
> _______________________________________________
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-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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