From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel <xen-devel@lists.xen.org>
Subject: Re: reading IOPL
Date: Thu, 3 May 2012 13:22:11 -0400 [thread overview]
Message-ID: <20120503172211.GE9992@phenom.dumpdata.com> (raw)
In-Reply-To: <4FA2C94802000078000816E3@nat28.tlf.novell.com>
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
next prev parent reply other threads:[~2012-05-03 17:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-03 16:07 reading IOPL Jan Beulich
2012-05-03 17:22 ` Konrad Rzeszutek Wilk [this message]
2012-05-04 7:09 ` Jan Beulich
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