[XenPPC] [xenppc-unstable] [POWERPC][XEN] Better explane the larx/stcx issue with interrupts

[Xen patchbot-xenppc-unstable <patchbot-xenppc-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
# Node ID 25442712f4cb2de72b1dd9dbdb471942c84ceca3
# Parent  1d50658481071d73564b4d722e3d3199104c481a
[POWERPC][XEN] Better explane the larx/stcx issue with interrupts

Signed-off-by: Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
---
 xen/arch/powerpc/powerpc64/exceptions.S |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletion(-)

diff -r 1d5065848107 -r 25442712f4cb xen/arch/powerpc/powerpc64/exceptions.S
--- a/xen/arch/powerpc/powerpc64/exceptions.S   Thu Sep 14 01:41:13 2006 -0400
+++ b/xen/arch/powerpc/powerpc64/exceptions.S   Thu Sep 14 10:17:23 2006 -0400
@@ -118,7 +118,11 @@ 1:
     mfspr r0, SPRN_HSPRG1
     std r0, UREGS_r13(r1)           /* save R13 from HSPRG1 */
 
-    /* Blow away any reservation according to 970 errata after saving CR */
+    /* Only _one_ larx is allowed at a time.  Any future use will be
+     * rejected until the earlier one (if any) completes.  Since we
+     * may have interrupted a larx in the Domain, or Xen we need to
+     * clear any larx that may currently exist.  We could probably
+     * skip which for hcalls */
     ldx r0, 0, r1
     stdcx. r0, 0, r1
 

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