powerpc: Use names rather than numbers for SPRGs (v2)

The kernel uses SPRG registers for various purposes, typically in
low level assembly code as scratch registers or to hold per-cpu
global infos such as the PACA or the current thread_info pointer.

We want to be able to easily shuffle the usage of those registers
as some implementations have specific constraints realted to some
of them, for example, some have userspace readable aliases, etc..
and the current choice isn't always the best.

This patch should not change any code generation, and replaces the
usage of SPRN_SPRGn everywhere in the kernel with a named replacement
and adds documentation next to the definition of the names as to
what those are used for on each processor family.

The only parts that still use the original numbers are bits of KVM
or suspend/resume code that just blindly needs to save/restore all
the SPRGs.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 9 insertions, 9 deletions

diff --git a/arch/powerpc/kvm/booke_interrupts.S b/arch/powerpc/kvm/booke_interrupts.S
index d0c6f841bbd1..380a78cf484d 100644
--- a/arch/powerpc/kvm/booke_interrupts.S
+++ b/arch/powerpc/kvm/booke_interrupts.S
@@ -56,8 +56,8 @@
 .macro KVM_HANDLER ivor_nr
 _GLOBAL(kvmppc_handler_\ivor_nr)
         /* Get pointer to vcpu and record exit number. */
-        mtspr   SPRN_SPRG0, r4
-        mfspr   r4, SPRN_SPRG1
+        mtspr   SPRN_SPRG_WSCRATCH0, r4
+        mfspr   r4, SPRN_SPRG_RVCPU
         stw     r5, VCPU_GPR(r5)(r4)
         stw     r6, VCPU_GPR(r6)(r4)
         mfctr   r5
@@ -95,7 +95,7 @@ _GLOBAL(kvmppc_handler_len)
 
 
 /* Registers:
- *  SPRG0: guest r4
+ *  SPRG_SCRATCH0: guest r4
  *  r4: vcpu pointer
  *  r5: KVM exit number
  */
@@ -181,7 +181,7 @@ _GLOBAL(kvmppc_resume_host)
         stw     r3, VCPU_LR(r4)
         mfxer   r3
         stw     r3, VCPU_XER(r4)
-        mfspr   r3, SPRN_SPRG0
+        mfspr   r3, SPRN_SPRG_RSCRATCH0
         stw     r3, VCPU_GPR(r4)(r4)
         mfspr   r3, SPRN_SRR0
         stw     r3, VCPU_PC(r4)
@@ -374,7 +374,7 @@ lightweight_exit:
         mtspr   SPRN_IVPR, r8
 
         /* Save vcpu pointer for the exception handlers. */
-        mtspr   SPRN_SPRG1, r4
+        mtspr   SPRN_SPRG_WVCPU, r4
 
         /* Can't switch the stack pointer until after IVPR is switched,
          * because host interrupt handlers would get confused. */
@@ -384,13 +384,13 @@ lightweight_exit:
         /* Host interrupt handlers may have clobbered these guest-readable
          * SPRGs, so we need to reload them here with the guest's values. */
         lwz     r3, VCPU_SPRG4(r4)
-        mtspr   SPRN_SPRG4, r3
+        mtspr   SPRN_SPRG4W, r3
         lwz     r3, VCPU_SPRG5(r4)
-        mtspr   SPRN_SPRG5, r3
+        mtspr   SPRN_SPRG5W, r3
         lwz     r3, VCPU_SPRG6(r4)
-        mtspr   SPRN_SPRG6, r3
+        mtspr   SPRN_SPRG6W, r3
         lwz     r3, VCPU_SPRG7(r4)
-        mtspr   SPRN_SPRG7, r3
+        mtspr   SPRN_SPRG7W, r3
 
 #ifdef CONFIG_KVM_EXIT_TIMING
         /* save enter time */