RE: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.
From: Christian Limpach
Date: Fri Feb 16 2007 - 05:27:59 EST
Jeremy Fitzhardinge wrote:
> Andrew Morton wrote:
> > On Thu, 15 Feb 2007 22:14:45 -0800 Dan Hecht
> <dhecht@xxxxxxxxxx> 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.
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