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 8b64a9dfb091f1eca8b7e58da82f1e7d1d5fe0ad ("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

3 files changed, 10 insertions, 8 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index e66d4ec04d9..fbfca5778b0 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/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? */
diff --git a/arch/powerpc/kvm/book3s_interrupts.S b/arch/powerpc/kvm/book3s_interrupts.S
index f779450cb07..3533c999194 100644
--- a/arch/powerpc/kvm/book3s_interrupts.S
+++ b/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 */
diff --git a/arch/powerpc/kvm/bookehv_interrupts.S b/arch/powerpc/kvm/bookehv_interrupts.S
index e4185f6b330..99635a37c78 100644
--- a/arch/powerpc/kvm/bookehv_interrupts.S
+++ b/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)