Re: [Xen-devel] XENFEAT_supervisor_mode_kernel ???

To:	<mukesh.rathor@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] XENFEAT_supervisor_mode_kernel ???
From:	Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date:	Thu, 20 Nov 2008 22:55:12 +0000
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On 20/11/08 22:42, "Mukesh Rathor" <mukesh.rathor@xxxxxxxxxx> wrote:

> I'm trying ot figure out what that's all about? I see in 64 PV domU, it's
> being checked prior to returning from syscall.  On the xen side, I see it tied
> to supervisor_mode_kernel, but the only info I find is changelog comment which
> suggests it's purpose is to allow dom0 run in ring 0... So why the check in a
> domU kernel?

It's useful if the hypervisor runs the guest kernel in ring 0. Current Xen
doesn't do that, but in future we may run 64-bit PV guests in HVM context as
that may actually be faster.

 -- Keir

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Re: [Xen-devel] XENFEAT_supervisor_mode_kernel ???