[PATCH] ppc64: Correct alignment for lppaca in paca_struct

From: Anton Blanchard
Date: Thu Dec 09 2004 - 09:52:19 EST

Hi Andrew,

Sorry, last patch was mangled in some way.

I think this is 2.6.10 material, as well as lparcfg it fixes a nasty
bug in our shared processor support (some cpus fail to recognise they
are in shared processor mode).



From: Will Schmidt <willschm@xxxxxxxxxx>

We found that we were failing register_vpa calls in cases where the lppaca
structure (part of the PACA) crosses a page boundary.

This was causing us (lparcfg specifically) some grief as the xSharedProc bit
was not being set.

The attached patch changes the alignment of the lppaca structure, and a few
comments so we understand why.

Signed-off-by: Will Schmidt <willschm@xxxxxxxxxx>
Signed-off-by: Anton Blanchard <anton@xxxxxxxxx>

diff -puN include/asm-ppc64/paca.h~vpa_align include/asm-ppc64/paca.h
--- foobar2/include/asm-ppc64/paca.h~vpa_align 2004-12-10 01:40:32.325580252 +1100
+++ foobar2-anton/include/asm-ppc64/paca.h 2004-12-10 01:41:14.558646921 +1100
@@ -99,11 +99,13 @@ struct paca_struct {
u64 exdsi[8]; /* used for linear mapping hash table misses */

- * iSeries structues which the hypervisor knows about - Not
- * sure if these particularly need to be cacheline aligned.
+ * iSeries structues which the hypervisor knows about -
+ * This structure should not cross a page boundary.
+ * The vpa_init/register_vpa call is now known to fail if the lppaca
+ * structure crosses a page boundary.
* The lppaca is also used on POWER5 pSeries boxes.
- struct ItLpPaca lppaca __attribute__((aligned(0x80)));
+ struct ItLpPaca lppaca __attribute__((aligned(0x400)));
struct ItLpRegSave reg_save;
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