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Re: [Xen-devel] how page faults are handled in paravirtualized xenguests

To: "Daniel Stodden" <stodden@xxxxxxxxxx>
Subject: Re: [Xen-devel] how page faults are handled in paravirtualized xenguests?
From: weiming <zephyr.zhao@xxxxxxxxx>
Date: Tue, 11 Mar 2008 10:37:35 -0500
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, tgh <wwwwww4187@xxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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and how can xen tell if the hypercall is from kernel space or user space in x86_64?

On Tue, Mar 11, 2008 at 9:43 AM, weiming <zephyr.zhao@xxxxxxxxx> wrote:
some material says that guest kernel runs in ring 1 and applications in ring 3. Is this for x86 32 ?

On Tue, Mar 11, 2008 at 2:21 AM, Daniel Stodden <stodden@xxxxxxxxxx> wrote:
On Tue, 2008-03-11 at 09:38 +0800, tgh wrote:
> hi
>   and that is ,in 64-bit,guest application entry into guestos kernel
> directly through SYSCALL,or  not?

no, you can't. programs use syscall to enter the kernel, and the kernel
is using syscall to enter xen. since you can only configure one entry
point at a time (and both xen and applications run in ring 3 anyway),
xen is handling all syscalls, then checks the context it was issued
from, and forwards the call to to the guest kernel if it was user code.

regards,
daniel

--
Daniel Stodden
LRR     -      Lehrstuhl für Rechnertechnik und Rechnerorganisation
Institut für Informatik der TU München             D-85748 Garching
http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
PGP Fingerprint: F5A4 1575 4C56 E26A 0B33  3D80 457E 82AE B0D8 735B




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