[PATCH v2 40/60] KVM: PPC: Book3S HV P9: Implement TM fastpath for guest entry/exit

[Nicholas Piggin]

If TM is not active, only TM register state needs to be saved and
restored, avoiding several mfmsr/mtmsrd instructions and improving
performance.

Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
 arch/powerpc/kvm/book3s_hv_p9_entry.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c 
b/arch/powerpc/kvm/book3s_hv_p9_entry.c
index 9ea70736f3d7..e52d8b040970 100644
--- a/arch/powerpc/kvm/book3s_hv_p9_entry.c
+++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c
@@ -289,8 +289,15 @@ bool load_vcpu_state(struct kvm_vcpu *vcpu,
 
        if (cpu_has_feature(CPU_FTR_TM) ||
            cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) {
-               kvmppc_restore_tm_hv(vcpu, vcpu->arch.shregs.msr, true);
-               ret = true;
+               unsigned long guest_msr = vcpu->arch.shregs.msr;
+               if (MSR_TM_ACTIVE(guest_msr)) {
+                       kvmppc_restore_tm_hv(vcpu, guest_msr, true);
+                       ret = true;
+               } else {
+                       mtspr(SPRN_TEXASR, vcpu->arch.texasr);
+                       mtspr(SPRN_TFHAR, vcpu->arch.tfhar);
+                       mtspr(SPRN_TFIAR, vcpu->arch.tfiar);
+               }
        }
 
        load_spr_state(vcpu, host_os_sprs);
@@ -316,8 +323,16 @@ void store_vcpu_state(struct kvm_vcpu *vcpu)
        vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);
 
        if (cpu_has_feature(CPU_FTR_TM) ||
-           cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))
-               kvmppc_save_tm_hv(vcpu, vcpu->arch.shregs.msr, true);
+           cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) {
+               unsigned long guest_msr = vcpu->arch.shregs.msr;
+               if (MSR_TM_ACTIVE(guest_msr)) {
+                       kvmppc_save_tm_hv(vcpu, guest_msr, true);
+               } else {
+                       vcpu->arch.texasr = mfspr(SPRN_TEXASR);
+                       vcpu->arch.tfhar = mfspr(SPRN_TFHAR);
+                       vcpu->arch.tfiar = mfspr(SPRN_TFIAR);
+               }
+       }
 }
 EXPORT_SYMBOL_GPL(store_vcpu_state);
 
-- 
2.23.0