powerpc/booke64: Use SPRG7 for VDSO

Previously SPRG3 was marked for use by both VDSO and critical
interrupts (though critical interrupts were not fully implemented).

In commit 8b64a9df ("powerpc/booke64:
Use SPRG0/3 scratch for bolted TLB miss & crit int"), Mihai Caraman
made an attempt to resolve this conflict by restoring the VDSO value
early in the critical interrupt, but this has some issues:

 - It's incompatible with EXCEPTION_COMMON which restores r13 from the
   by-then-overwritten scratch (this cost me some debugging time).
 - It forces critical exceptions to be a special case handled
   differently from even machine check and debug level exceptions.
 - It didn't occur to me that it was possible to make this work at all
   (by doing a final "ld r13, PACA_EXCRIT+EX_R13(r13)") until after
   I made (most of) this patch. :-)

It might be worth investigating using a load rather than SPRG on return
from all exceptions (except TLB misses where the scratch never leaves
the SPRG) -- it could save a few cycles.  Until then, let's stick with
SPRG for all exceptions.

Since we cannot use SPRG4-7 for scratch without corrupting the state of
a KVM guest, move VDSO to SPRG7 on book3e.  Since neither SPRG4-7 nor
critical interrupts exist on book3s, SPRG3 is still used for VDSO
there.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: Mihai Caraman <mihai.caraman@freescale.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: kvm-ppc@vger.kernel.org

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

@@ -46,9 +46,8 @@
 #define EX_CR		(1 * 8)
 #define EX_R10		(2 * 8)
 #define EX_R11		(3 * 8)
-#define EX_R13		(4 * 8)
-#define EX_R14		(5 * 8)
-#define EX_R15		(6 * 8)
+#define EX_R14		(4 * 8)
+#define EX_R15		(5 * 8)
 
 /*
  * The TLB miss exception uses different slots.

arch/powerpc/include/asm/kvm_booke_hv_asm.h

@@ -36,19 +36,12 @@
  *   *(r8 + GPR11) = saved r11
  *
  * 64-bit host
- * Expected inputs (GEN/GDBELL/DBG/MC exception types):
+ * Expected inputs (GEN/GDBELL/DBG/CRIT/MC exception types):
  *  r10 = saved CR
  *  r13 = PACA_POINTER
  *  *(r13 + PACA_EX##type + EX_R10) = saved r10
  *  *(r13 + PACA_EX##type + EX_R11) = saved r11
  *  SPRN_SPRG_##type##_SCRATCH = saved r13
- *
-  * Expected inputs (CRIT exception type):
- *  r10 = saved CR
- *  r13 = PACA_POINTER
- *  *(r13 + PACA_EX##type + EX_R10) = saved r10
- *  *(r13 + PACA_EX##type + EX_R11) = saved r11
- *  *(r13 + PACA_EX##type + EX_R13) = saved r13
  *
  * Expected inputs (TLB exception type):
  *  r10 = saved CR

arch/powerpc/include/asm/paca.h

@@ -146,7 +146,7 @@ struct paca_struct {
 	u8 io_sync;			/* writel() needs spin_unlock sync */
 	u8 irq_work_pending;		/* IRQ_WORK interrupt while soft-disable */
 	u8 nap_state_lost;		/* NV GPR values lost in power7_idle */
-	u64 sprg3;			/* Saved user-visible sprg */
+	u64 sprg_vdso;			/* Saved user-visible sprg */
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	u64 tm_scratch;                 /* TM scratch area for reclaim */
 #endif

arch/powerpc/include/asm/reg.h

@@ -577,9 +577,13 @@
 #define SPRN_SPRG3	0x113	/* Special Purpose Register General 3 */
 #define SPRN_USPRG3	0x103	/* SPRG3 userspace read */
 #define SPRN_SPRG4	0x114	/* Special Purpose Register General 4 */
+#define SPRN_USPRG4	0x104	/* SPRG4 userspace read */
 #define SPRN_SPRG5	0x115	/* Special Purpose Register General 5 */
+#define SPRN_USPRG5	0x105	/* SPRG5 userspace read */
 #define SPRN_SPRG6	0x116	/* Special Purpose Register General 6 */
+#define SPRN_USPRG6	0x106	/* SPRG6 userspace read */
 #define SPRN_SPRG7	0x117	/* Special Purpose Register General 7 */
+#define SPRN_USPRG7	0x107	/* SPRG7 userspace read */
 #define SPRN_SRR0	0x01A	/* Save/Restore Register 0 */
 #define SPRN_SRR1	0x01B	/* Save/Restore Register 1 */
 #define   SRR1_ISI_NOPT		0x40000000 /* ISI: Not found in hash */
@@ -879,11 +883,10 @@
  * 64-bit embedded
  *	- SPRG0 generic exception scratch
  *	- SPRG2 TLB exception stack
- *	- SPRG3 critical exception scratch and
- *        CPU and NUMA node for VDSO getcpu (user visible)
+ *	- SPRG3 critical exception scratch (user visible, sorry!)
  *	- SPRG4 unused (user visible)
  *	- SPRG6 TLB miss scratch (user visible, sorry !)
- *	- SPRG7 critical exception scratch
+ *	- SPRG7 CPU and NUMA node for VDSO getcpu (user visible)
  *	- SPRG8 machine check exception scratch
  *	- SPRG9 debug exception scratch
  *
@@ -940,6 +943,8 @@
 #define SPRN_SPRG_SCRATCH0	SPRN_SPRG2
 #define SPRN_SPRG_HPACA		SPRN_HSPRG0
 #define SPRN_SPRG_HSCRATCH0	SPRN_HSPRG1
+#define SPRN_SPRG_VDSO_READ	SPRN_USPRG3
+#define SPRN_SPRG_VDSO_WRITE	SPRN_SPRG3
 
 #define GET_PACA(rX)					\
 	BEGIN_FTR_SECTION_NESTED(66);			\
@@ -983,6 +988,8 @@
 #define SPRN_SPRG_TLB_SCRATCH	SPRN_SPRG6
 #define SPRN_SPRG_GEN_SCRATCH	SPRN_SPRG0
 #define SPRN_SPRG_GDBELL_SCRATCH SPRN_SPRG_GEN_SCRATCH
+#define SPRN_SPRG_VDSO_READ	SPRN_USPRG7
+#define SPRN_SPRG_VDSO_WRITE	SPRN_SPRG7
 
 #define SET_PACA(rX)	mtspr	SPRN_SPRG_PACA,rX
 #define GET_PACA(rX)	mfspr	rX,SPRN_SPRG_PACA

arch/powerpc/kernel/asm-offsets.c

@@ -253,7 +253,7 @@ int main(void)
 	DEFINE(PACA_SYSTEM_TIME, offsetof(struct paca_struct, system_time));
 	DEFINE(PACA_TRAP_SAVE, offsetof(struct paca_struct, trap_save));
 	DEFINE(PACA_NAPSTATELOST, offsetof(struct paca_struct, nap_state_lost));
-	DEFINE(PACA_SPRG3, offsetof(struct paca_struct, sprg3));
+	DEFINE(PACA_SPRG_VDSO, offsetof(struct paca_struct, sprg_vdso));
 #endif /* CONFIG_PPC64 */
 
 	/* RTAS */

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

@@ -55,7 +55,6 @@
 	mfspr	r13,SPRN_SPRG_PACA;	/* get PACA */			    \
 	std	r10,PACA_EX##type+EX_R10(r13);				    \
 	std	r11,PACA_EX##type+EX_R11(r13);				    \
-	PROLOG_STORE_RESTORE_SCRATCH_##type;				    \
 	mfcr	r10;			/* save CR */			    \
 	mfspr	r11,SPRN_##type##_SRR1;/* what are we coming from */	    \
 	DO_KVM	intnum,SPRN_##type##_SRR1;    /* KVM hook */		    \
@@ -116,20 +115,6 @@
 #define GDBELL_EXCEPTION_PROLOG(n, intnum, addition)			    \
 	EXCEPTION_PROLOG(n, intnum, GDBELL, addition##_GDBELL(n))
 
-/*
- * Store user-visible scratch in PACA exception slots and restore proper value
- */
-#define PROLOG_STORE_RESTORE_SCRATCH_GEN
-#define PROLOG_STORE_RESTORE_SCRATCH_GDBELL
-#define PROLOG_STORE_RESTORE_SCRATCH_DBG
-#define PROLOG_STORE_RESTORE_SCRATCH_MC
-
-#define PROLOG_STORE_RESTORE_SCRATCH_CRIT				    \
-	mfspr	r10,SPRN_SPRG_CRIT_SCRATCH;	/* get r13 */		    \
-	std	r10,PACA_EXCRIT+EX_R13(r13);				    \
-	ld	r11,PACA_SPRG3(r13);					    \
-	mtspr	SPRN_SPRG_CRIT_SCRATCH,r11;
-
 /* Variants of the "addition" argument for the prolog
  */
 #define PROLOG_ADDITION_NONE_GEN(n)
@@ -529,7 +514,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 	mtcr	r10
 	ld	r10,PACA_EXCRIT+EX_R10(r13)	/* restore registers */
 	ld	r11,PACA_EXCRIT+EX_R11(r13)
-	ld	r13,PACA_EXCRIT+EX_R13(r13)
+	mfspr	r13,SPRN_SPRG_CRIT_SCRATCH
 	rfci
 
 	/* Normal debug exception */
@@ -542,7 +527,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 	/* Now we mash up things to make it look like we are coming on a
 	 * normal exception
 	 */
-	ld	r15,PACA_EXCRIT+EX_R13(r13)
+	mfspr	r15,SPRN_SPRG_CRIT_SCRATCH
 	mtspr	SPRN_SPRG_GEN_SCRATCH,r15
 	mfspr	r14,SPRN_DBSR
 	EXCEPTION_COMMON(0xd00, PACA_EXCRIT, INTS_DISABLE)

arch/powerpc/kernel/vdso.c

@@ -715,8 +715,8 @@ int vdso_getcpu_init(void)
 	unsigned long cpu, node, val;
 
 	/*
-	 * SPRG3 contains the CPU in the bottom 16 bits and the NUMA node in
-	 * the next 16 bits. The VDSO uses this to implement getcpu().
+	 * SPRG_VDSO contains the CPU in the bottom 16 bits and the NUMA node
+	 * in the next 16 bits.  The VDSO uses this to implement getcpu().
 	 */
 	cpu = get_cpu();
 	WARN_ON_ONCE(cpu > 0xffff);
@@ -725,8 +725,8 @@ int vdso_getcpu_init(void)
 	WARN_ON_ONCE(node > 0xffff);
 
 	val = (cpu & 0xfff) | ((node & 0xffff) << 16);
-	mtspr(SPRN_SPRG3, val);
-	get_paca()->sprg3 = val;
+	mtspr(SPRN_SPRG_VDSO_WRITE, val);
+	get_paca()->sprg_vdso = val;
 
 	put_cpu();
 

arch/powerpc/kernel/vdso32/getcpu.S

@@ -29,7 +29,7 @@
  */
 V_FUNCTION_BEGIN(__kernel_getcpu)
   .cfi_startproc
-	mfspr	r5,SPRN_USPRG3
+	mfspr	r5,SPRN_SPRG_VDSO_READ
 	cmpdi	cr0,r3,0
 	cmpdi	cr1,r4,0
 	clrlwi  r6,r5,16

arch/powerpc/kernel/vdso64/getcpu.S

@@ -29,7 +29,7 @@
  */
 V_FUNCTION_BEGIN(__kernel_getcpu)
   .cfi_startproc
-	mfspr	r5,SPRN_USPRG3
+	mfspr	r5,SPRN_SPRG_VDSO_READ
 	cmpdi	cr0,r3,0
 	cmpdi	cr1,r4,0
 	clrlwi  r6,r5,16

arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -75,8 +75,8 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
 
 	/* Restore SPRG3 */
-	ld	r3,PACA_SPRG3(r13)
-	mtspr	SPRN_SPRG3,r3
+	ld	r3,PACA_SPRG_VDSO(r13)
+	mtspr	SPRN_SPRG_VDSO_WRITE,r3
 
 	/* Reload the host's PMU registers */
 	ld	r3, PACALPPACAPTR(r13)	/* is the host using the PMU? */

arch/powerpc/kvm/book3s_interrupts.S

@@ -153,8 +153,8 @@ kvm_start_lightweight:
 	 * Reload kernel SPRG3 value.
 	 * No need to save guest value as usermode can't modify SPRG3.
 	 */
-	ld	r3, PACA_SPRG3(r13)
-	mtspr	SPRN_SPRG3, r3
+	ld	r3, PACA_SPRG_VDSO(r13)
+	mtspr	SPRN_SPRG_VDSO_WRITE, r3
 #endif /* CONFIG_PPC_BOOK3S_64 */
 
 	/* R7 = vcpu */

arch/powerpc/kvm/bookehv_interrupts.S

@@ -229,11 +229,7 @@
 	stw	r10, VCPU_CR(r4)
 	PPC_STL r11, VCPU_GPR(R4)(r4)
 	PPC_STL	r5, VCPU_GPR(R5)(r4)
-	.if \type == EX_CRIT
-	PPC_LL	r5, (\paca_ex + EX_R13)(r13)
-	.else
 	mfspr	r5, \scratch
-	.endif
 	PPC_STL	r6, VCPU_GPR(R6)(r4)
 	PPC_STL	r8, VCPU_GPR(R8)(r4)
 	PPC_STL	r9, VCPU_GPR(R9)(r4)
@@ -435,10 +431,16 @@ _GLOBAL(kvmppc_resume_host)
 	PPC_STL	r5, VCPU_LR(r4)
 	mfspr	r7, SPRN_SPRG5
 	stw	r3, VCPU_VRSAVE(r4)
+#ifdef CONFIG_64BIT
+	PPC_LL	r3, PACA_SPRG_VDSO(r13)
+#endif
 	PPC_STD(r6, VCPU_SHARED_SPRG4, r11)
 	mfspr	r8, SPRN_SPRG6
 	PPC_STD(r7, VCPU_SHARED_SPRG5, r11)
 	mfspr	r9, SPRN_SPRG7
+#ifdef CONFIG_64BIT
+	mtspr	SPRN_SPRG_VDSO_WRITE, r3
+#endif
 	PPC_STD(r8, VCPU_SHARED_SPRG6, r11)
 	mfxer	r3
 	PPC_STD(r9, VCPU_SHARED_SPRG7, r11)