KVM: PPC: Book3S HV P9: Don't restore PSSCR if not needed

This also moves the PSSCR update in nested entry to avoid a SPR
scoreboard stall.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-42-npiggin@gmail.com

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 7d48aa8..9da27f1 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -3889,7 +3889,9 @@ static int kvmhv_vcpu_entry_p9_nested(struct kvm_vcpu *vcpu, u64 time_limit, uns
        if (unlikely(load_vcpu_state(vcpu, &host_os_sprs)))
                msr = mfmsr(); /* TM restore can update msr */
 
-       mtspr(SPRN_PSSCR_PR, vcpu->arch.psscr);
+       if (vcpu->arch.psscr != host_psscr)
+               mtspr(SPRN_PSSCR_PR, vcpu->arch.psscr);
+
        kvmhv_save_hv_regs(vcpu, &hvregs);
        hvregs.lpcr = lpcr;
        vcpu->arch.regs.msr = vcpu->arch.shregs.msr;
@@ -3930,7 +3932,6 @@ static int kvmhv_vcpu_entry_p9_nested(struct kvm_vcpu *vcpu, u64 time_limit, uns
        vcpu->arch.shregs.dar = mfspr(SPRN_DAR);
        vcpu->arch.shregs.dsisr = mfspr(SPRN_DSISR);
        vcpu->arch.psscr = mfspr(SPRN_PSSCR_PR);
-       mtspr(SPRN_PSSCR_PR, host_psscr);
 
        store_vcpu_state(vcpu);
 
@@ -3943,6 +3944,8 @@ static int kvmhv_vcpu_entry_p9_nested(struct kvm_vcpu *vcpu, u64 time_limit, uns
        timer_rearm_host_dec(*tb);
 
        restore_p9_host_os_sprs(vcpu, &host_os_sprs);
+       if (vcpu->arch.psscr != host_psscr)
+               mtspr(SPRN_PSSCR_PR, host_psscr);
 
        return trap;
 }

diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c b/arch/powerpc/kvm/book3s_hv_p9_entry.c
index 0f34101..eae9d80 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv_p9_entry.c
+++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c
@@ -649,6 +649,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
        unsigned long host_dawr0;
        unsigned long host_dawrx0;
        unsigned long host_psscr;
+       unsigned long host_hpsscr;
        unsigned long host_pidr;
        unsigned long host_dawr1;
        unsigned long host_dawrx1;
@@ -666,7 +667,9 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
 
        host_hfscr = mfspr(SPRN_HFSCR);
        host_ciabr = mfspr(SPRN_CIABR);
-       host_psscr = mfspr(SPRN_PSSCR);
+       host_psscr = mfspr(SPRN_PSSCR_PR);
+       if (cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))
+               host_hpsscr = mfspr(SPRN_PSSCR);
        host_pidr = mfspr(SPRN_PID);
 
        if (dawr_enabled()) {
@@ -750,8 +753,14 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
        if (vcpu->arch.ciabr != host_ciabr)
                mtspr(SPRN_CIABR, vcpu->arch.ciabr);
 
-       mtspr(SPRN_PSSCR, vcpu->arch.psscr | PSSCR_EC |
-             (local_paca->kvm_hstate.fake_suspend << PSSCR_FAKE_SUSPEND_LG));
+
+       if (cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) {
+               mtspr(SPRN_PSSCR, vcpu->arch.psscr | PSSCR_EC |
+                     (local_paca->kvm_hstate.fake_suspend << PSSCR_FAKE_SUSPEND_LG));
+       } else {
+               if (vcpu->arch.psscr != host_psscr)
+                       mtspr(SPRN_PSSCR_PR, vcpu->arch.psscr);
+       }
 
        mtspr(SPRN_HFSCR, vcpu->arch.hfscr);
 
@@ -957,7 +966,7 @@ tm_return_to_guest:
 
        vcpu->arch.ic = mfspr(SPRN_IC);
        vcpu->arch.pid = mfspr(SPRN_PID);
-       vcpu->arch.psscr = mfspr(SPRN_PSSCR) & PSSCR_GUEST_VIS;
+       vcpu->arch.psscr = mfspr(SPRN_PSSCR_PR);
 
        vcpu->arch.shregs.sprg0 = mfspr(SPRN_SPRG0);
        vcpu->arch.shregs.sprg1 = mfspr(SPRN_SPRG1);
@@ -1003,9 +1012,12 @@ tm_return_to_guest:
        mtspr(SPRN_PURR, local_paca->kvm_hstate.host_purr);
        mtspr(SPRN_SPURR, local_paca->kvm_hstate.host_spurr);
 
-       /* Preserve PSSCR[FAKE_SUSPEND] until we've called kvmppc_save_tm_hv */
-       mtspr(SPRN_PSSCR, host_psscr |
-             (local_paca->kvm_hstate.fake_suspend << PSSCR_FAKE_SUSPEND_LG));
+       if (cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) {
+               /* Preserve PSSCR[FAKE_SUSPEND] until we've called kvmppc_save_tm_hv */
+               mtspr(SPRN_PSSCR, host_hpsscr |
+                     (local_paca->kvm_hstate.fake_suspend << PSSCR_FAKE_SUSPEND_LG));
+       }
+
        mtspr(SPRN_HFSCR, host_hfscr);
        if (vcpu->arch.ciabr != host_ciabr)
                mtspr(SPRN_CIABR, host_ciabr);