In message [ref] you wrote
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quoted

Index: linux-2.6-ozlabs/include/asm-powerpc/processor.h
===================================================================

--- linux-2.6-ozlabs.orig/include/asm-powerpc/processor.h
+++ linux-2.6-ozlabs/include/asm-powerpc/processor.h

@@ -78,6 +78,7 @@ extern long kernel_thread(int (*fn)(void

/* Lazy FPU handling on uni-processor */
extern struct task_struct *last_task_used_math;
extern struct task_struct *last_task_used_altivec;
+extern struct task_struct *last_task_used_vsx;
extern struct task_struct *last_task_used_spe;

#ifdef CONFIG_PPC32

@@ -136,8 +137,13 @@ typedef struct {

	unsigned long seg;
} mm_segment_t;

+#ifdef CONFIG_VSX
+#define TS_FPR(i) fpvsr.fp[i].fpr
+#define TS_FPRSTART fpvsr.fp
+#else
#define TS_FPR(i) fpr[i]
#define TS_FPRSTART fpr
+#endif

struct thread_struct {
	unsigned long	ksp;		/* Kernel stack pointer */

@@ -155,8 +161,19 @@ struct thread_struct {

	unsigned long	dbcr0;		/* debug control register values */
	unsigned long	dbcr1;
#endif
+#ifdef CONFIG_VSX
+	/* First 32 VSX registers (overlap with fpr[32]) */
+	union {
+		struct {
+			double fpr;
+			double vsrlow;
+		} fp[32];
+		vector128	vsr[32];
+	} fpvsr __attribute__((aligned(16)));

Do we really need a union here?  what would happen if you just changed  
the type of fpr[32] from double to vector if #CONFIG_VSX?

I really dont like the union and think we can just make the storage  
look opaque which is the key.  I doubt we every really care about  
using fpr[] as a double in the kernel.

I did something similar to this for the first cut of this patch, but it
made the code accessing this structure much less readable.

Personally, I think the union is good as it represents the true
structure of what it's storing.

Also, the attribute is redundant, vector is already aligned(16).

Ok, I'll remove.

Mikey

quoted

+#else
	double		fpr[32];	/* Complete floating point set */
-	struct {			/* fpr ... fpscr must be contiguous */
+#endif
+	struct {

		unsigned int pad;
		unsigned int val;	/* Floating point status */

@@ -176,6 +193,10 @@ struct thread_struct {

	unsigned long	vrsave;
	int		used_vr;	/* set if process has used altivec */
#endif /* CONFIG_ALTIVEC */
+#ifdef CONFIG_VSX
+	/* VSR status */
+	int		used_vsr;	/* set if process has used altivec */
+#endif /* CONFIG_VSX */
#ifdef CONFIG_SPE
	unsigned long	evr[32];	/* upper 32-bits of SPE regs */
	u64		acc;		/* Accumulator */

@@ -200,7 +221,11 @@ struct thread_struct {

	.fpexc_mode = MSR_FE0 | MSR_FE1, \
}
#else
+#ifdef CONFIG_VSX
+#define	FPVSR_INIT_THREAD .fpvsr = { .vsr = 0, }
+#else
#define	FPVSR_INIT_THREAD .fpr = {0}
+#endif
#define INIT_THREAD  { \
	.ksp = INIT_SP, \
	.ksp_limit = INIT_SP_LIMIT, \

@@ -293,5 +318,9 @@ static inline void prefetchw(const void

#endif /* __KERNEL__ */
#endif /* __ASSEMBLY__ */
+#ifdef CONFIG_VSX
+#define TS_FPRSPACING 2
+#else
#define TS_FPRSPACING 1
+#endif
#endif /* _ASM_POWERPC_PROCESSOR_H */
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