powerpc: Add VSX context save/restore, ptrace and signal support

This patch extends the floating point save and restore code to use the
VSX load/stores when VSX is available.  This will make FP context
save/restore marginally slower on FP only code, when VSX is available,
as it has to load/store 128bits rather than just 64bits.

Mixing FP, VMX and VSX code will get constant architected state.

The signals interface is extended to enable access to VSR 0-31
doubleword 1 after discussions with tool chain maintainers.  Backward
compatibility is maintained.

The ptrace interface is also extended to allow access to VSR 0-31 full
registers.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/entry_64.S

@@ -353,6 +353,11 @@ _GLOBAL(_switch)
 	mflr	r20		/* Return to switch caller */
 	mfmsr	r22
 	li	r0, MSR_FP
+#ifdef CONFIG_VSX
+BEGIN_FTR_SECTION
+	oris	r0,r0,MSR_VSX@h	/* Disable VSX */
+END_FTR_SECTION_IFSET(CPU_FTR_VSX)
+#endif /* CONFIG_VSX */
 #ifdef CONFIG_ALTIVEC
 BEGIN_FTR_SECTION
 	oris	r0,r0,MSR_VEC@h	/* Disable altivec */

arch/powerpc/kernel/fpu.S

@@ -57,6 +57,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_VSX);					\
 _GLOBAL(load_up_fpu)
 	mfmsr	r5
 	ori	r5,r5,MSR_FP
+#ifdef CONFIG_VSX
+BEGIN_FTR_SECTION
+	oris	r5,r5,MSR_VSX@h
+END_FTR_SECTION_IFSET(CPU_FTR_VSX)
+#endif
 	SYNC
 	MTMSRD(r5)			/* enable use of fpu now */
 	isync
@@ -73,7 +78,7 @@ _GLOBAL(load_up_fpu)
 	beq	1f
 	toreal(r4)
 	addi	r4,r4,THREAD		/* want last_task_used_math->thread */
-	SAVE_32FPRS(0, r4)
+	SAVE_32FPVSRS(0, r5, r4)
 	mffs	fr0
 	stfd	fr0,THREAD_FPSCR(r4)
 	PPC_LL	r5,PT_REGS(r4)
@@ -100,7 +105,7 @@ _GLOBAL(load_up_fpu)
 #endif
 	lfd	fr0,THREAD_FPSCR(r5)
 	MTFSF_L(fr0)
-	REST_32FPRS(0, r5)
+	REST_32FPVSRS(0, r4, r5)
 #ifndef CONFIG_SMP
 	subi	r4,r5,THREAD
 	fromreal(r4)
@@ -119,6 +124,11 @@ _GLOBAL(load_up_fpu)
 _GLOBAL(giveup_fpu)
 	mfmsr	r5
 	ori	r5,r5,MSR_FP
+#ifdef CONFIG_VSX
+BEGIN_FTR_SECTION
+	oris	r5,r5,MSR_VSX@h
+END_FTR_SECTION_IFSET(CPU_FTR_VSX)
+#endif
 	SYNC_601
 	ISYNC_601
 	MTMSRD(r5)			/* enable use of fpu now */
@@ -129,7 +139,7 @@ _GLOBAL(giveup_fpu)
 	addi	r3,r3,THREAD	        /* want THREAD of task */
 	PPC_LL	r5,PT_REGS(r3)
 	PPC_LCMPI	0,r5,0
-	SAVE_32FPRS(0, r3)
+	SAVE_32FPVSRS(0, r4 ,r3)
 	mffs	fr0
 	stfd	fr0,THREAD_FPSCR(r3)
 	beq	1f

arch/powerpc/kernel/head_64.S

@@ -278,6 +278,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE)
 	. = 0xf20
 	b	altivec_unavailable_pSeries
 
+	. = 0xf40
+	b	vsx_unavailable_pSeries
+
 #ifdef CONFIG_CBE_RAS
 	HSTD_EXCEPTION_PSERIES(0x1200, cbe_system_error)
 #endif /* CONFIG_CBE_RAS */
@@ -297,6 +300,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE)
 	/* moved from 0xf00 */
 	STD_EXCEPTION_PSERIES(., performance_monitor)
 	STD_EXCEPTION_PSERIES(., altivec_unavailable)
+	STD_EXCEPTION_PSERIES(., vsx_unavailable)
 
 /*
  * An interrupt came in while soft-disabled; clear EE in SRR1,
@@ -836,6 +840,67 @@ _STATIC(load_up_altivec)
 	blr
 #endif /* CONFIG_ALTIVEC */
 
+	.align	7
+	.globl vsx_unavailable_common
+vsx_unavailable_common:
+	EXCEPTION_PROLOG_COMMON(0xf40, PACA_EXGEN)
+#ifdef CONFIG_VSX
+BEGIN_FTR_SECTION
+	bne	.load_up_vsx
+1:
+END_FTR_SECTION_IFSET(CPU_FTR_VSX)
+#endif
+	bl	.save_nvgprs
+	addi	r3,r1,STACK_FRAME_OVERHEAD
+	ENABLE_INTS
+	bl	.vsx_unavailable_exception
+	b	.ret_from_except
+
+#ifdef CONFIG_VSX
+/*
+ * load_up_vsx(unused, unused, tsk)
+ * Disable VSX for the task which had it previously,
+ * and save its vector registers in its thread_struct.
+ * Reuse the fp and vsx saves, but first check to see if they have
+ * been saved already.
+ * On entry: r13 == 'current' && last_task_used_vsx != 'current'
+ */
+_STATIC(load_up_vsx)
+/* Load FP and VSX registers if they haven't been done yet */
+	andi.	r5,r12,MSR_FP
+	beql+	load_up_fpu		/* skip if already loaded */
+	andis.	r5,r12,MSR_VEC@h
+	beql+	load_up_altivec		/* skip if already loaded */
+
+#ifndef CONFIG_SMP
+	ld	r3,last_task_used_vsx@got(r2)
+	ld	r4,0(r3)
+	cmpdi	0,r4,0
+	beq	1f
+	/* Disable VSX for last_task_used_vsx */
+	addi	r4,r4,THREAD
+	ld	r5,PT_REGS(r4)
+	ld	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
+	lis	r6,MSR_VSX@h
+	andc	r6,r4,r6
+	std	r6,_MSR-STACK_FRAME_OVERHEAD(r5)
+1:
+#endif /* CONFIG_SMP */
+	ld	r4,PACACURRENT(r13)
+	addi	r4,r4,THREAD		/* Get THREAD */
+	li	r6,1
+	stw	r6,THREAD_USED_VSR(r4) /* ... also set thread used vsr */
+	/* enable use of VSX after return */
+	oris	r12,r12,MSR_VSX@h
+	std	r12,_MSR(r1)
+#ifndef CONFIG_SMP
+	/* Update last_task_used_math to 'current' */
+	ld	r4,PACACURRENT(r13)
+	std	r4,0(r3)
+#endif /* CONFIG_SMP */
+	b	fast_exception_return
+#endif /* CONFIG_VSX */
+
 /*
  * Hash table stuff
  */

arch/powerpc/kernel/misc_64.S

@@ -506,6 +506,39 @@ _GLOBAL(giveup_altivec)
 
 #endif /* CONFIG_ALTIVEC */
 
+#ifdef CONFIG_VSX
+/*
+ * giveup_vsx(tsk)
+ * Disable VSX for the task given as the argument,
+ * and save the vector registers in its thread_struct.
+ * Enables the VSX for use in the kernel on return.
+ */
+_GLOBAL(giveup_vsx)
+	mfmsr	r5
+	oris	r5,r5,MSR_VSX@h
+	mtmsrd	r5			/* enable use of VSX now */
+	isync
+
+	cmpdi	0,r3,0
+	beqlr-				/* if no previous owner, done */
+	addi	r3,r3,THREAD		/* want THREAD of task */
+	ld	r5,PT_REGS(r3)
+	cmpdi	0,r5,0
+	beq	1f
+	ld	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
+	lis	r3,MSR_VSX@h
+	andc	r4,r4,r3		/* disable VSX for previous task */
+	std	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
+1:
+#ifndef CONFIG_SMP
+	li	r5,0
+	ld	r4,last_task_used_vsx@got(r2)
+	std	r5,0(r4)
+#endif /* CONFIG_SMP */
+	blr
+
+#endif /* CONFIG_VSX */
+
 /* kexec_wait(phys_cpu)
  *
  * wait for the flag to change, indicating this kernel is going away but

arch/powerpc/kernel/ppc32.h

@@ -120,6 +120,7 @@ struct mcontext32 {
 	elf_fpregset_t		mc_fregs;
 	unsigned int		mc_pad[2];
 	elf_vrregset_t32	mc_vregs __attribute__((__aligned__(16)));
+	elf_vsrreghalf_t32      mc_vsregs __attribute__((__aligned__(16)));
 };
 
 struct ucontext32 { 

arch/powerpc/kernel/ppc_ksyms.c

@@ -102,6 +102,9 @@ EXPORT_SYMBOL(giveup_fpu);
 #ifdef CONFIG_ALTIVEC
 EXPORT_SYMBOL(giveup_altivec);
 #endif /* CONFIG_ALTIVEC */
+#ifdef CONFIG_VSX
+EXPORT_SYMBOL(giveup_vsx);
+#endif /* CONFIG_VSX */
 #ifdef CONFIG_SPE
 EXPORT_SYMBOL(giveup_spe);
 #endif /* CONFIG_SPE */

arch/powerpc/kernel/process.c

@@ -53,6 +53,7 @@ extern unsigned long _get_SP(void);
 #ifndef CONFIG_SMP
 struct task_struct *last_task_used_math = NULL;
 struct task_struct *last_task_used_altivec = NULL;
+struct task_struct *last_task_used_vsx = NULL;
 struct task_struct *last_task_used_spe = NULL;
 #endif
 
@@ -106,11 +107,23 @@ EXPORT_SYMBOL(enable_kernel_fp);
 
 int dump_task_fpu(struct task_struct *tsk, elf_fpregset_t *fpregs)
 {
+#ifdef CONFIG_VSX
+	int i;
+	elf_fpreg_t *reg;
+#endif
+
 	if (!tsk->thread.regs)
 		return 0;
 	flush_fp_to_thread(current);
 
+#ifdef CONFIG_VSX
+	reg = (elf_fpreg_t *)fpregs;
+	for (i = 0; i < ELF_NFPREG - 1; i++, reg++)
+		*reg = tsk->thread.TS_FPR(i);
+	memcpy(reg, &tsk->thread.fpscr, sizeof(elf_fpreg_t));
+#else
 	memcpy(fpregs, &tsk->thread.TS_FPR(0), sizeof(*fpregs));
+#endif
 
 	return 1;
 }
@@ -149,7 +162,7 @@ void flush_altivec_to_thread(struct task_struct *tsk)
 	}
 }
 
-int dump_task_altivec(struct task_struct *tsk, elf_vrregset_t *vrregs)
+int dump_task_altivec(struct task_struct *tsk, elf_vrreg_t *vrregs)
 {
 	/* ELF_NVRREG includes the VSCR and VRSAVE which we need to save
 	 * separately, see below */
@@ -179,6 +192,80 @@ int dump_task_altivec(struct task_struct *tsk, elf_vrregset_t *vrregs)
 }
 #endif /* CONFIG_ALTIVEC */
 
+#ifdef CONFIG_VSX
+#if 0
+/* not currently used, but some crazy RAID module might want to later */
+void enable_kernel_vsx(void)
+{
+	WARN_ON(preemptible());
+
+#ifdef CONFIG_SMP
+	if (current->thread.regs && (current->thread.regs->msr & MSR_VSX))
+		giveup_vsx(current);
+	else
+		giveup_vsx(NULL);	/* just enable vsx for kernel - force */
+#else
+	giveup_vsx(last_task_used_vsx);
+#endif /* CONFIG_SMP */
+}
+EXPORT_SYMBOL(enable_kernel_vsx);
+#endif
+
+void flush_vsx_to_thread(struct task_struct *tsk)
+{
+	if (tsk->thread.regs) {
+		preempt_disable();
+		if (tsk->thread.regs->msr & MSR_VSX) {
+#ifdef CONFIG_SMP
+			BUG_ON(tsk != current);
+#endif
+			giveup_vsx(tsk);
+		}
+		preempt_enable();
+	}
+}
+
+/*
+ * This dumps the lower half 64bits of the first 32 VSX registers.
+ * This needs to be called with dump_task_fp and dump_task_altivec to
+ * get all the VSX state.
+ */
+int dump_task_vsx(struct task_struct *tsk, elf_vrreg_t *vrregs)
+{
+	elf_vrreg_t *reg;
+	double buf[32];
+	int i;
+
+	if (tsk == current)
+		flush_vsx_to_thread(tsk);
+
+	reg = (elf_vrreg_t *)vrregs;
+
+	for (i = 0; i < 32 ; i++)
+		buf[i] = current->thread.fpr[i][TS_VSRLOWOFFSET];
+	memcpy(reg, buf, sizeof(buf));
+
+	return 1;
+}
+#endif /* CONFIG_VSX */
+
+int dump_task_vector(struct task_struct *tsk, elf_vrregset_t *vrregs)
+{
+	int rc = 0;
+	elf_vrreg_t *regs = (elf_vrreg_t *)vrregs;
+#ifdef CONFIG_ALTIVEC
+	rc = dump_task_altivec(tsk, regs);
+	if (rc)
+		return rc;
+	regs += ELF_NVRREG;
+#endif
+
+#ifdef CONFIG_VSX
+	rc = dump_task_vsx(tsk, regs);
+#endif
+	return rc;
+}
+
 #ifdef CONFIG_SPE
 
 void enable_kernel_spe(void)
@@ -233,6 +320,10 @@ void discard_lazy_cpu_state(void)
 	if (last_task_used_altivec == current)
 		last_task_used_altivec = NULL;
 #endif /* CONFIG_ALTIVEC */
+#ifdef CONFIG_VSX
+	if (last_task_used_vsx == current)
+		last_task_used_vsx = NULL;
+#endif /* CONFIG_VSX */
 #ifdef CONFIG_SPE
 	if (last_task_used_spe == current)
 		last_task_used_spe = NULL;
@@ -297,6 +388,10 @@ struct task_struct *__switch_to(struct task_struct *prev,
 	if (prev->thread.regs && (prev->thread.regs->msr & MSR_VEC))
 		giveup_altivec(prev);
 #endif /* CONFIG_ALTIVEC */
+#ifdef CONFIG_VSX
+	if (prev->thread.regs && (prev->thread.regs->msr & MSR_VSX))
+		giveup_vsx(prev);
+#endif /* CONFIG_VSX */
 #ifdef CONFIG_SPE
 	/*
 	 * If the previous thread used spe in the last quantum
@@ -317,6 +412,10 @@ struct task_struct *__switch_to(struct task_struct *prev,
 	if (new->thread.regs && last_task_used_altivec == new)
 		new->thread.regs->msr |= MSR_VEC;
 #endif /* CONFIG_ALTIVEC */
+#ifdef CONFIG_VSX
+	if (new->thread.regs && last_task_used_vsx == new)
+		new->thread.regs->msr |= MSR_VSX;
+#endif /* CONFIG_VSX */
 #ifdef CONFIG_SPE
 	/* Avoid the trap.  On smp this this never happens since
 	 * we don't set last_task_used_spe
@@ -417,6 +516,8 @@ static struct regbit {
 	{MSR_EE,	"EE"},
 	{MSR_PR,	"PR"},
 	{MSR_FP,	"FP"},
+	{MSR_VEC,	"VEC"},
+	{MSR_VSX,	"VSX"},
 	{MSR_ME,	"ME"},
 	{MSR_IR,	"IR"},
 	{MSR_DR,	"DR"},
@@ -534,6 +635,7 @@ void prepare_to_copy(struct task_struct *tsk)
 {
 	flush_fp_to_thread(current);
 	flush_altivec_to_thread(current);
+	flush_vsx_to_thread(current);
 	flush_spe_to_thread(current);
 }
 
@@ -689,6 +791,9 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
 #endif
 
 	discard_lazy_cpu_state();
+#ifdef CONFIG_VSX
+	current->thread.used_vsr = 0;
+#endif
 	memset(current->thread.fpr, 0, sizeof(current->thread.fpr));
 	current->thread.fpscr.val = 0;
 #ifdef CONFIG_ALTIVEC