[RFC PATCH 01/10] KVM: PPC: BOOK3S: PR: Fix PURR and SPURR emulation

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

We definitely don't need to emulate mtspr, because both the registers
are hypervisor resource.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/kvm_book3s.h |  2 --
 arch/powerpc/include/asm/kvm_host.h   |  4 ++--
 arch/powerpc/kvm/book3s_emulate.c     | 16 ++++++++--------
 arch/powerpc/kvm/book3s_pr.c          | 10 ++++++++++
 4 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index bc23b1ba7980..396448afa38b 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -83,8 +83,6 @@ struct kvmppc_vcpu_book3s {
 	u64 sdr1;
 	u64 hior;
 	u64 msr_mask;
-	u64 purr_offset;
-	u64 spurr_offset;
 #ifdef CONFIG_PPC_BOOK3S_32
 	u32 vsid_pool[VSID_POOL_SIZE];
 	u32 vsid_next;
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 9a0cdb2c9d58..0a3785271f34 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -506,8 +506,8 @@ struct kvm_vcpu_arch {
 #ifdef CONFIG_BOOKE
 	u32 decar;
 #endif
-	u32 tbl;
-	u32 tbu;
+	/* Time base value when we entered the guest */
+	u64 entry_tb;
 	u32 tcr;
 	ulong tsr; /* we need to perform set/clr_bits() which requires ulong */
 	u32 ivor[64];
diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index a7d54aa203d0..e1f1e5e16449 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -422,12 +422,6 @@ int kvmppc_core_emulate_mtspr_pr(struct kvm_vcpu *vcpu, int sprn, ulong spr_val)
 		    (mfmsr() & MSR_HV))
 			vcpu->arch.hflags |= BOOK3S_HFLAG_DCBZ32;
 		break;
-	case SPRN_PURR:
-		to_book3s(vcpu)->purr_offset = spr_val - get_tb();
-		break;
-	case SPRN_SPURR:
-		to_book3s(vcpu)->spurr_offset = spr_val - get_tb();
-		break;
 	case SPRN_GQR0:
 	case SPRN_GQR1:
 	case SPRN_GQR2:
@@ -523,10 +517,16 @@ int kvmppc_core_emulate_mfspr_pr(struct kvm_vcpu *vcpu, int sprn, ulong *spr_val
 		*spr_val = 0;
 		break;
 	case SPRN_PURR:
-		*spr_val = get_tb() + to_book3s(vcpu)->purr_offset;
+		/*
+		 * On exit we would have updated purr
+		 */
+		*spr_val = vcpu->arch.purr;
 		break;
 	case SPRN_SPURR:
-		*spr_val = get_tb() + to_book3s(vcpu)->purr_offset;
+		/*
+		 * On exit we would have updated spurr
+		 */
+		*spr_val = vcpu->arch.spurr;
 		break;
 	case SPRN_GQR0:
 	case SPRN_GQR1:
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index fdcbabdfb709..02231f5193c2 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -115,6 +115,11 @@ void kvmppc_copy_to_svcpu(struct kvmppc_book3s_shadow_vcpu *svcpu,
 	svcpu->lr  = vcpu->arch.lr;
 	svcpu->pc  = vcpu->arch.pc;
 	svcpu->in_use = true;
+	/*
+	 * Now also save the current time base value. We use this
+	 * to find the guest purr and spurr value.
+	 */
+	vcpu->arch.entry_tb = get_tb();
 }
 
 /* Copy data touched by real-mode code from shadow vcpu back to vcpu */
@@ -161,6 +166,11 @@ void kvmppc_copy_from_svcpu(struct kvm_vcpu *vcpu,
 
 out:
 	preempt_enable();
+	/*
+	 * Update purr and spurr using time base
+	 */
+	vcpu->arch.purr += get_tb() - vcpu->arch.entry_tb;
+	vcpu->arch.spurr += get_tb() - vcpu->arch.entry_tb;
 }
 
 static int kvmppc_core_check_requests_pr(struct kvm_vcpu *vcpu)
-- 
1.8.5.3