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From: "Christian Limpach" <Christian.Limpach@xensource.com>
To: "Jeremy Fitzhardinge" <jeremy@goop.org>,
	"Andrew Morton" <akpm@linux-foundation.org>
Cc: "Chris Wright" <chrisw@sous-sol.org>, "Andi Kleen" <ak@muc.de>,
	"Keir Fraser" <Keir.Fraser@cl.cam.ac.uk>,
	<xen-devel@lists.xensource.com>,
	"Ian Pratt" <Ian.Pratt@xensource.com>,
	<virtualization@lists.osdl.org>,
	"Steven Hand" <steven.hand@cl.cam.ac.uk>,
	<linux-kernel@vger.kernel.org>
Subject: RE: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.
Date: Fri, 16 Feb 2007 02:00:39 -0800	[thread overview]
Message-ID: <BBC437B5B077FF46935BA1D8C9A2172A01EBEBF4@exch2.ad.xensource.com> (raw)

Jeremy Fitzhardinge wrote:
> Andrew Morton wrote:
> > On Thu, 15 Feb 2007 22:14:45 -0800 Dan Hecht 
> <dhecht@vmware.com> wrote:
> >
> >   
> >>>  config PREEMPT
> >>>  	bool "Preemptible Kernel (Low-Latency Desktop)"
> >>> +	depends on !XEN
> >>>  	help
> >>>  	  This option reduces the latency of the kernel by making
> >>>  	  all kernel code (that is not executing in a critical section)
> >>>
> >>>       
> >
> > Oh, so that's why it doesn't break when CONFIG_PREEMPT=y.  
> In which case
> > that preempt_disable() I spotted is wrong-and-unneeded.
> >
> > Why doesn't Xen work with preemption??
> >   
> 
> I've forgotten the details.  Ian?  Keir?  Steven?  Maybe it 
> can be done.

With CONFIG_PREEMPT, we can have preempted threads reference machine
addresses across save/restore.  After restore, these machine addresses
will be incorrect.

    Christian

WARNING: multiple messages have this Message-ID (diff)
From: "Christian Limpach" <Christian.Limpach@xensource.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: xen-devel@lists.xensource.com, virtualization@lists.osdl.org,
	Steven Hand <steven.hand@cl.cam.ac.uk>,
	linux-kernel@vger.kernel.org, Chris Wright <chrisw@sous-sol.org>,
	Andi Kleen <ak@muc.de>, Ian Pratt <Ian.Pratt@xensource.com>
Subject: RE: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.
Date: Fri, 16 Feb 2007 02:00:39 -0800	[thread overview]
Message-ID: <BBC437B5B077FF46935BA1D8C9A2172A01EBEBF4@exch2.ad.xensource.com> (raw)

Jeremy Fitzhardinge wrote:
> Andrew Morton wrote:
> > On Thu, 15 Feb 2007 22:14:45 -0800 Dan Hecht 
> <dhecht@vmware.com> wrote:
> >
> >   
> >>>  config PREEMPT
> >>>  	bool "Preemptible Kernel (Low-Latency Desktop)"
> >>> +	depends on !XEN
> >>>  	help
> >>>  	  This option reduces the latency of the kernel by making
> >>>  	  all kernel code (that is not executing in a critical section)
> >>>
> >>>       
> >
> > Oh, so that's why it doesn't break when CONFIG_PREEMPT=y.  
> In which case
> > that preempt_disable() I spotted is wrong-and-unneeded.
> >
> > Why doesn't Xen work with preemption??
> >   
> 
> I've forgotten the details.  Ian?  Keir?  Steven?  Maybe it 
> can be done.

With CONFIG_PREEMPT, we can have preempted threads reference machine
addresses across save/restore.  After restore, these machine addresses
will be incorrect.

    Christian

             reply	other threads:[~2007-02-16 10:27 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-16 10:00 Christian Limpach [this message]
2007-02-16 10:00 ` [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options Christian Limpach
2007-02-16 10:09 ` Andrew Morton
2007-02-16 10:09   ` Andrew Morton
2007-02-16 10:47   ` Keir Fraser
2007-02-16 10:47   ` Keir Fraser
2007-02-16 10:47     ` Keir Fraser
2007-02-16 10:54     ` Andrew Morton
2007-02-16 10:54       ` Andrew Morton
2007-02-16 11:03       ` Keir Fraser
2007-02-16 11:03       ` Keir Fraser
2007-02-16 11:03         ` Keir Fraser
2007-02-16 17:46         ` [Xen-devel] " Jeremy Fitzhardinge
2007-02-16 17:46           ` Jeremy Fitzhardinge
2007-02-16 19:00           ` [Xen-devel] " Keir Fraser
2007-02-16 19:00           ` Keir Fraser
2007-02-16 19:00             ` Keir Fraser
2007-02-16 19:24             ` [Xen-devel] " Jeremy Fitzhardinge
2007-02-16 19:24               ` Jeremy Fitzhardinge
2007-02-16 21:51             ` [Xen-devel] " Zachary Amsden
2007-02-16 21:51               ` Zachary Amsden
2007-02-16 22:38               ` [Xen-devel] " Dan Hecht
2007-02-17 15:06                 ` Rik van Riel
2007-02-17 15:06                   ` Rik van Riel
2007-02-16 19:00           ` [Xen-devel] " Keir Fraser
2007-02-16 11:03       ` Keir Fraser
2007-02-16 10:47   ` Keir Fraser

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