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xen-devel
[Xen-devel] Re: [RFC PATCH 16/33] Add support for Xen to entry.S.
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To: |
Arjan van de Ven <arjan@xxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [RFC PATCH 16/33] Add support for Xen to entry.S. |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Tue, 18 Jul 2006 13:04:10 -0700 |
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Cc: |
Andrew Morton <akpm@xxxxxxxx>, Zachary Amsden <zach@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>, Ian Pratt <ian.pratt@xxxxxxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Andi Kleen <ak@xxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx, Christian Limpach <Christian.Limpach@xxxxxxxxxxxx> |
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Thu, 20 Jul 2006 05:25:01 -0700 |
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Arjan van de Ven wrote:
On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote:
+#ifndef CONFIG_XEN
movl %cr0, %eax
testl $0x4, %eax # EM (math emulation bit)
- jne device_not_available_emulate
- preempt_stop
- call math_state_restore
- jmp ret_from_exception
-device_not_available_emulate:
+ je device_available_emulate
pushl $0 # temporary storage for ORIG_EIP
CFI_ADJUST_CFA_OFFSET 4
call math_emulate
addl $4, %esp
CFI_ADJUST_CFA_OFFSET -4
+ jmp ret_from_exception
+device_available_emulate:
+#endif
Hi,
can you explain what this chunk is for? It appears to be for the non-xen
case due to the ifndef, yet it seems to visibly change the code for
that... that deserves an explanation for sure ...
This inverts the logic of the test so that the lines:
preempt_stop
call math_state_restore
jmp ret_from_exception
can be hoisted out of the ifdef and shared in the Xen and non-Xen cases.
J
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