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

[weiming <zephyr.zhao@xxxxxxxxx>]

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

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