From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: reading IOPL
Date: Thu, 3 May 2012 13:22:11 -0400
Message-ID: <20120503172211.GE9992@phenom.dumpdata.com>
References: <4FA2C94802000078000816E3@nat28.tlf.novell.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Content-Disposition: inline
In-Reply-To: <4FA2C94802000078000816E3@nat28.tlf.novell.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel <xen-devel@lists.xen.org>
List-Id: xen-devel@lists.xenproject.org

On Thu, May 03, 2012 at 05:07:04PM +0100, Jan Beulich wrote:
> Both Linux and Xen offer only ways to set the IOPL. While on native Linux
> this is not a problem since user mode code can read the IOPL by inspecting
> EFLAGS, on Xen this would always yield zero.
> 
> Now X folks appear to be using save-modify-restore cycles in some newer
> code, and this obviously breaks under Xen, as they would restore IOPL 0

This is in the KMS drivers or in the user-land Xorg?

> even when IOPL 3 was in effect before.
> 
> Since the only way to read the IOPL is xc_vcpu_getcontext() (i.e.
> XEN_DOMCTL_getvcpucontext), I wonder whether we shouldn't add
> e.g. a "get" counterpart to PHYSDEVOP_set_iopl.
> 
> Or am I overlooking some other access mechanism?
> 
> Jan
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel