powerpc: In HV mode, use HSPRG0 for PACA

When running in Hypervisor mode (arch 2.06 or later), we store the PACA
in HSPRG0 instead of SPRG1. The architecture specifies that SPRGs may be
lost during a "nap" power management operation (though they aren't
currently on POWER7) and this enables use of SPRG1 by KVM guests.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/exception-64s.h

@@ -57,7 +57,7 @@
 	addi	reg,reg,(label)-_stext;	/* virt addr of handler ... */
 
 #define EXCEPTION_PROLOG_1(area)					\
-	mfspr	r13,SPRN_SPRG_PACA;	/* get paca address into r13 */	\
+	GET_PACA(r13);							\
 	std	r9,area+EX_R9(r13);	/* save r9 - r12 */		\
 	std	r10,area+EX_R10(r13);					\
 	std	r11,area+EX_R11(r13);					\
@@ -174,7 +174,7 @@ label##_pSeries:							\
 	HMT_MEDIUM;							\
 	DO_KVM	n;							\
 	mtspr	SPRN_SPRG_SCRATCH0,r13;	/* save r13 */			\
-	mfspr	r13,SPRN_SPRG_PACA;	/* get paca address into r13 */	\
+	GET_PACA(r13);							\
 	std	r9,PACA_EXGEN+EX_R9(r13);	/* save r9, r10 */	\
 	std	r10,PACA_EXGEN+EX_R10(r13);				\
 	lbz	r10,PACASOFTIRQEN(r13);					\

arch/powerpc/include/asm/reg.h

@@ -715,12 +715,15 @@
  * SPRG usage:
  *
  * All 64-bit:
- *	- SPRG1 stores PACA pointer
+ *	- SPRG1 stores PACA pointer except 64-bit server in
+ *        HV mode in which case it is HSPRG0
  *
  * 64-bit server:
  *	- SPRG0 unused (reserved for HV on Power4)
  *	- SPRG2 scratch for exception vectors
  *	- SPRG3 unused (user visible)
+ *      - HSPRG0 stores PACA in HV mode
+ *      - HSPRG1 scratch for "HV" exceptions
  *
  * 64-bit embedded
  *	- SPRG0 generic exception scratch
@@ -783,6 +786,22 @@
 
 #ifdef CONFIG_PPC_BOOK3S_64
 #define SPRN_SPRG_SCRATCH0	SPRN_SPRG2
+#define SPRN_SPRG_HPACA		SPRN_HSPRG0
+#define SPRN_SPRG_HSCRATCH0	SPRN_HSPRG1
+
+#define GET_PACA(rX)					\
+	BEGIN_FTR_SECTION_NESTED(66);			\
+	mfspr	rX,SPRN_SPRG_PACA;			\
+	FTR_SECTION_ELSE_NESTED(66);			\
+	mfspr	rX,SPRN_SPRG_HPACA;			\
+	ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_HVMODE_206, 66)
+
+#define SET_PACA(rX)					\
+	BEGIN_FTR_SECTION_NESTED(66);			\
+	mtspr	SPRN_SPRG_PACA,rX;			\
+	FTR_SECTION_ELSE_NESTED(66);			\
+	mtspr	SPRN_SPRG_HPACA,rX;			\
+	ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_HVMODE_206, 66)
 #endif
 
 #ifdef CONFIG_PPC_BOOK3E_64
@@ -792,6 +811,10 @@
 #define SPRN_SPRG_TLB_EXFRAME	SPRN_SPRG2
 #define SPRN_SPRG_TLB_SCRATCH	SPRN_SPRG6
 #define SPRN_SPRG_GEN_SCRATCH	SPRN_SPRG0
+
+#define SET_PACA(rX)	mtspr	SPRN_SPRG_PACA,rX
+#define GET_PACA(rX)	mfspr	rX,SPRN_SPRG_PACA
+
 #endif
 
 #ifdef CONFIG_PPC_BOOK3S_32
@@ -842,6 +865,8 @@
 #define SPRN_SPRG_SCRATCH1	SPRN_SPRG1
 #endif
 
+
+
 /*
  * An mtfsf instruction with the L bit set. On CPUs that support this a
  * full 64bits of FPSCR is restored and on other CPUs the L bit is ignored.

arch/powerpc/kernel/entry_64.S

@@ -838,7 +838,7 @@ _GLOBAL(enter_rtas)
 
 _STATIC(rtas_return_loc)
 	/* relocation is off at this point */
-	mfspr	r4,SPRN_SPRG_PACA	/* Get PACA */
+	GET_PACA(r4)
 	clrldi	r4,r4,2			/* convert to realmode address */
 
 	bcl	20,31,$+4
@@ -869,7 +869,7 @@ _STATIC(rtas_restore_regs)
 	REST_8GPRS(14, r1)		/* Restore the non-volatiles */
 	REST_10GPRS(22, r1)		/* ditto */
 
-	mfspr	r13,SPRN_SPRG_PACA
+	GET_PACA(r13)
 
 	ld	r4,_CCR(r1)
 	mtcr	r4

arch/powerpc/kernel/exceptions-64s.S

@@ -53,7 +53,7 @@ data_access_pSeries:
 	DO_KVM	0x300
 	mtspr	SPRN_SPRG_SCRATCH0,r13
 BEGIN_FTR_SECTION
-	mfspr	r13,SPRN_SPRG_PACA
+	GET_PACA(r13)
 	std	r9,PACA_EXSLB+EX_R9(r13)
 	std	r10,PACA_EXSLB+EX_R10(r13)
 	mfspr	r10,SPRN_DAR
@@ -82,7 +82,7 @@ data_access_slb_pSeries:
 	HMT_MEDIUM
 	DO_KVM	0x380
 	mtspr	SPRN_SPRG_SCRATCH0,r13
-	mfspr	r13,SPRN_SPRG_PACA		/* get paca address into r13 */
+	GET_PACA(r13)
 	std	r3,PACA_EXSLB+EX_R3(r13)
 	mfspr	r3,SPRN_DAR
 	std	r9,PACA_EXSLB+EX_R9(r13)	/* save r9 - r12 */
@@ -121,7 +121,7 @@ instruction_access_slb_pSeries:
 	HMT_MEDIUM
 	DO_KVM	0x480
 	mtspr	SPRN_SPRG_SCRATCH0,r13
-	mfspr	r13,SPRN_SPRG_PACA		/* get paca address into r13 */
+	GET_PACA(r13)
 	std	r3,PACA_EXSLB+EX_R3(r13)
 	mfspr	r3,SPRN_SRR0		/* SRR0 is faulting address */
 	std	r9,PACA_EXSLB+EX_R9(r13)	/* save r9 - r12 */
@@ -165,7 +165,7 @@ BEGIN_FTR_SECTION
 	beq-	1f
 END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE)
 	mr	r9,r13
-	mfspr	r13,SPRN_SPRG_PACA
+	GET_PACA(r13)
 	mfspr	r11,SPRN_SRR0
 	ld	r12,PACAKBASE(r13)
 	ld	r10,PACAKMSR(r13)

arch/powerpc/kernel/head_64.S

@@ -228,7 +228,7 @@ generic_secondary_common_init:
 	mr	r3,r24			/* not found, copy phys to r3	 */
 	b	.kexec_wait		/* next kernel might do better	 */
 
-2:	mtspr	SPRN_SPRG_PACA,r13	/* Save vaddr of paca in an SPRG */
+2:	SET_PACA(r13)
 #ifdef CONFIG_PPC_BOOK3E
 	addi	r12,r13,PACA_EXTLB	/* and TLB exc frame in another  */
 	mtspr	SPRN_SPRG_TLB_EXFRAME,r12
@@ -534,7 +534,7 @@ _GLOBAL(pmac_secondary_start)
 	ld	r4,0(r4)		/* Get base vaddr of paca array	*/
 	mulli	r13,r24,PACA_SIZE	/* Calculate vaddr of right paca */
 	add	r13,r13,r4		/* for this processor.		*/
-	mtspr	SPRN_SPRG_PACA,r13	/* Save vaddr of paca in an SPRG*/
+	SET_PACA(r13)			/* Save vaddr of paca in an SPRG*/
 
 	/* Mark interrupts soft and hard disabled (they might be enabled
 	 * in the PACA when doing hotplug)

arch/powerpc/kernel/paca.c

@@ -156,11 +156,22 @@ void __init initialise_paca(struct paca_struct *new_paca, int cpu)
 /* Put the paca pointer into r13 and SPRG_PACA */
 void setup_paca(struct paca_struct *new_paca)
 {
+	/* Setup r13 */
 	local_paca = new_paca;
-	mtspr(SPRN_SPRG_PACA, local_paca);
+
 #ifdef CONFIG_PPC_BOOK3E
+	/* On Book3E, initialize the TLB miss exception frames */
 	mtspr(SPRN_SPRG_TLB_EXFRAME, local_paca->extlb);
+#else
+	/* In HV mode, we setup both HPACA and PACA to avoid problems
+	 * if we do a GET_PACA() before the feature fixups have been
+	 * applied
+	 */
+	if (cpu_has_feature(CPU_FTR_HVMODE_206))
+		mtspr(SPRN_SPRG_HPACA, local_paca);
 #endif
+	mtspr(SPRN_SPRG_PACA, local_paca);
+
 }
 
 static int __initdata paca_size;

arch/powerpc/kvm/book3s_rmhandlers.S

@@ -35,9 +35,7 @@
 
 #if defined(CONFIG_PPC_BOOK3S_64)
 
-#define LOAD_SHADOW_VCPU(reg)				\
-	mfspr	reg, SPRN_SPRG_PACA
-
+#define LOAD_SHADOW_VCPU(reg)	GET_PACA(reg)					
 #define SHADOW_VCPU_OFF		PACA_KVM_SVCPU
 #define MSR_NOIRQ		MSR_KERNEL & ~(MSR_IR | MSR_DR)
 #define FUNC(name) 		GLUE(.,name)