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[Xen-devel] Re: [RFC PATCH 15/33] move segment checks to subarch

Arjan van de Ven wrote:
On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote:
plain text document attachment (i386-segments)
We allow for the fact that the guest kernel may not run in ring 0.
This requires some abstraction in a few places when setting %cs or
checking privilege level (user vs kernel).

-       regs.xcs = __KERNEL_CS;
+       regs.xcs = get_kernel_cs();


wouldn't this patch be simpler if __KERNEL_CS just became the macro that
currently is get_kernel_cs() for the XEN case? then code like this
doesn't need changing at all...

The tradeoff is that then you can't use __KERNEL_CS is assembler code, and it is used in entry.S to detect NMI / debug trap workarounds - which don't actually need to be paravirtualized, as it is easier to hide the nasty cases which cause those side effects.


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