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[Xen-ia64-devel] [PATCH]: makes b2-b5 fixed registers

from [Tristan Gingold]

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To:	Alex Williamson <alex.williamson@xxxxxx>, Xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	[Xen-ia64-devel] [PATCH]: makes b2-b5 fixed registers
From:	Tristan Gingold <tgingold@xxxxxxx>
Date:	Sun, 18 Feb 2007 16:35:59 +0100
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Hi,

Currently most registers are either fixed (eg: f12-f127) or saved on entry
in Xen (see minstate.h).
There are however a few exceptions: ec, lc, b2-b5.  These registers are
available by the compiler (but not scratch) and saved by save_switch_stack.
These registers can't be easily written to vcpu_guest_context (unless we
want to use unwind) which makes implementation of debugger impossible.

I will work on extending vcpu_guest_context soon.
During my preliminary work I remaked using objdump that b2-b5 were never used
by C code.  Therefore I can mark them as fixed without preformance impact.

Tristan.

bregs.diff
Description: Text document

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