KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests

This creates an alternative guest entry/exit path which is used for
radix guests on POWER9 systems when we have indep_threads_mode=Y.  In
these circumstances there is exactly one vcpu per vcore and there is
no coordination required between vcpus or vcores; the vcpu can enter
the guest without needing to synchronize with anything else.

The new fast path is implemented almost entirely in C in book3s_hv.c
and runs with the MMU on until the guest is entered.  On guest exit
we use the existing path until the point where we are committed to
exiting the guest (as distinct from handling an interrupt in the
low-level code and returning to the guest) and we have pulled the
guest context from the XIVE.  At that point we check a flag in the
stack frame to see whether we came in via the old path and the new
path; if we came in via the new path then we go back to C code to do
the rest of the process of saving the guest context and restoring the
host context.

The C code is split into separate functions for handling the
OS-accessible state and the hypervisor state, with the idea that the
latter can be replaced by a hypercall when we implement nested
virtualization.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
[mpe: Fix CONFIG_ALTIVEC=n build]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 432 insertions, 1 deletions

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 0e17593ee6e3..4befa5a812fe 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -3080,6 +3080,273 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
 }
 
 /*
+ * Load up hypervisor-mode registers on P9.
+ */
+static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit)
+{
+	struct kvmppc_vcore *vc = vcpu->arch.vcore;
+	s64 hdec;
+	u64 tb, purr, spurr;
+	int trap;
+	unsigned long host_hfscr = mfspr(SPRN_HFSCR);
+	unsigned long host_ciabr = mfspr(SPRN_CIABR);
+	unsigned long host_dawr = mfspr(SPRN_DAWR);
+	unsigned long host_dawrx = mfspr(SPRN_DAWRX);
+	unsigned long host_psscr = mfspr(SPRN_PSSCR);
+	unsigned long host_pidr = mfspr(SPRN_PID);
+
+	hdec = time_limit - mftb();
+	if (hdec < 0)
+		return BOOK3S_INTERRUPT_HV_DECREMENTER;
+	mtspr(SPRN_HDEC, hdec);
+
+	if (vc->tb_offset) {
+		u64 new_tb = mftb() + vc->tb_offset;
+		mtspr(SPRN_TBU40, new_tb);
+		tb = mftb();
+		if ((tb & 0xffffff) < (new_tb & 0xffffff))
+			mtspr(SPRN_TBU40, new_tb + 0x1000000);
+		vc->tb_offset_applied = vc->tb_offset;
+	}
+
+	if (vc->pcr)
+		mtspr(SPRN_PCR, vc->pcr);
+	mtspr(SPRN_DPDES, vc->dpdes);
+	mtspr(SPRN_VTB, vc->vtb);
+
+	local_paca->kvm_hstate.host_purr = mfspr(SPRN_PURR);
+	local_paca->kvm_hstate.host_spurr = mfspr(SPRN_SPURR);
+	mtspr(SPRN_PURR, vcpu->arch.purr);
+	mtspr(SPRN_SPURR, vcpu->arch.spurr);
+
+	if (cpu_has_feature(CPU_FTR_DAWR)) {
+		mtspr(SPRN_DAWR, vcpu->arch.dawr);
+		mtspr(SPRN_DAWRX, vcpu->arch.dawrx);
+	}
+	mtspr(SPRN_CIABR, vcpu->arch.ciabr);
+	mtspr(SPRN_IC, vcpu->arch.ic);
+	mtspr(SPRN_PID, vcpu->arch.pid);
+
+	mtspr(SPRN_PSSCR, vcpu->arch.psscr | PSSCR_EC |
+	      (local_paca->kvm_hstate.fake_suspend << PSSCR_FAKE_SUSPEND_LG));
+
+	mtspr(SPRN_HFSCR, vcpu->arch.hfscr);
+
+	mtspr(SPRN_SPRG0, vcpu->arch.shregs.sprg0);
+	mtspr(SPRN_SPRG1, vcpu->arch.shregs.sprg1);
+	mtspr(SPRN_SPRG2, vcpu->arch.shregs.sprg2);
+	mtspr(SPRN_SPRG3, vcpu->arch.shregs.sprg3);
+
+	mtspr(SPRN_AMOR, ~0UL);
+
+	mtspr(SPRN_LPCR, vc->lpcr);
+	isync();
+
+	kvmppc_xive_push_vcpu(vcpu);
+
+	mtspr(SPRN_SRR0, vcpu->arch.shregs.srr0);
+	mtspr(SPRN_SRR1, vcpu->arch.shregs.srr1);
+
+	trap = __kvmhv_vcpu_entry_p9(vcpu);
+
+	/* Advance host PURR/SPURR by the amount used by guest */
+	purr = mfspr(SPRN_PURR);
+	spurr = mfspr(SPRN_SPURR);
+	mtspr(SPRN_PURR, local_paca->kvm_hstate.host_purr +
+	      purr - vcpu->arch.purr);
+	mtspr(SPRN_SPURR, local_paca->kvm_hstate.host_spurr +
+	      spurr - vcpu->arch.spurr);
+	vcpu->arch.purr = purr;
+	vcpu->arch.spurr = spurr;
+
+	vcpu->arch.ic = mfspr(SPRN_IC);
+	vcpu->arch.pid = mfspr(SPRN_PID);
+	vcpu->arch.psscr = mfspr(SPRN_PSSCR) & PSSCR_GUEST_VIS;
+
+	vcpu->arch.shregs.sprg0 = mfspr(SPRN_SPRG0);
+	vcpu->arch.shregs.sprg1 = mfspr(SPRN_SPRG1);
+	vcpu->arch.shregs.sprg2 = mfspr(SPRN_SPRG2);
+	vcpu->arch.shregs.sprg3 = mfspr(SPRN_SPRG3);
+
+	mtspr(SPRN_PSSCR, host_psscr);
+	mtspr(SPRN_HFSCR, host_hfscr);
+	mtspr(SPRN_CIABR, host_ciabr);
+	mtspr(SPRN_DAWR, host_dawr);
+	mtspr(SPRN_DAWRX, host_dawrx);
+	mtspr(SPRN_PID, host_pidr);
+
+	/*
+	 * Since this is radix, do a eieio; tlbsync; ptesync sequence in
+	 * case we interrupted the guest between a tlbie and a ptesync.
+	 */
+	asm volatile("eieio; tlbsync; ptesync");
+
+	mtspr(SPRN_LPID, vcpu->kvm->arch.host_lpid);	/* restore host LPID */
+	isync();
+
+	vc->dpdes = mfspr(SPRN_DPDES);
+	vc->vtb = mfspr(SPRN_VTB);
+	mtspr(SPRN_DPDES, 0);
+	if (vc->pcr)
+		mtspr(SPRN_PCR, 0);
+
+	if (vc->tb_offset_applied) {
+		u64 new_tb = mftb() - vc->tb_offset_applied;
+		mtspr(SPRN_TBU40, new_tb);
+		tb = mftb();
+		if ((tb & 0xffffff) < (new_tb & 0xffffff))
+			mtspr(SPRN_TBU40, new_tb + 0x1000000);
+		vc->tb_offset_applied = 0;
+	}
+
+	mtspr(SPRN_HDEC, 0x7fffffff);
+	mtspr(SPRN_LPCR, vcpu->kvm->arch.host_lpcr);
+
+	return trap;
+}
+
+/*
+ * Virtual-mode guest entry for POWER9 and later when the host and
+ * guest are both using the radix MMU.  The LPIDR has already been set.
+ */
+int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit)
+{
+	struct kvmppc_vcore *vc = vcpu->arch.vcore;
+	unsigned long host_dscr = mfspr(SPRN_DSCR);
+	unsigned long host_tidr = mfspr(SPRN_TIDR);
+	unsigned long host_iamr = mfspr(SPRN_IAMR);
+	s64 dec;
+	u64 tb;
+	int trap, save_pmu;
+
+	dec = mfspr(SPRN_DEC);
+	tb = mftb();
+	if (dec < 512)
+		return BOOK3S_INTERRUPT_HV_DECREMENTER;
+	local_paca->kvm_hstate.dec_expires = dec + tb;
+	if (local_paca->kvm_hstate.dec_expires < time_limit)
+		time_limit = local_paca->kvm_hstate.dec_expires;
+
+	vcpu->arch.ceded = 0;
+
+	kvmhv_save_host_pmu();		/* saves it to PACA kvm_hstate */
+
+	kvmppc_subcore_enter_guest();
+
+	vc->entry_exit_map = 1;
+	vc->in_guest = 1;
+
+	if (vcpu->arch.vpa.pinned_addr) {
+		struct lppaca *lp = vcpu->arch.vpa.pinned_addr;
+		u32 yield_count = be32_to_cpu(lp->yield_count) + 1;
+		lp->yield_count = cpu_to_be32(yield_count);
+		vcpu->arch.vpa.dirty = 1;
+	}
+
+	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);
+
+	kvmhv_load_guest_pmu(vcpu);
+
+	msr_check_and_set(MSR_FP | MSR_VEC | MSR_VSX);
+	load_fp_state(&vcpu->arch.fp);
+#ifdef CONFIG_ALTIVEC
+	load_vr_state(&vcpu->arch.vr);
+#endif
+
+	mtspr(SPRN_DSCR, vcpu->arch.dscr);
+	mtspr(SPRN_IAMR, vcpu->arch.iamr);
+	mtspr(SPRN_PSPB, vcpu->arch.pspb);
+	mtspr(SPRN_FSCR, vcpu->arch.fscr);
+	mtspr(SPRN_TAR, vcpu->arch.tar);
+	mtspr(SPRN_EBBHR, vcpu->arch.ebbhr);
+	mtspr(SPRN_EBBRR, vcpu->arch.ebbrr);
+	mtspr(SPRN_BESCR, vcpu->arch.bescr);
+	mtspr(SPRN_WORT, vcpu->arch.wort);
+	mtspr(SPRN_TIDR, vcpu->arch.tid);
+	mtspr(SPRN_DAR, vcpu->arch.shregs.dar);
+	mtspr(SPRN_DSISR, vcpu->arch.shregs.dsisr);
+	mtspr(SPRN_AMR, vcpu->arch.amr);
+	mtspr(SPRN_UAMOR, vcpu->arch.uamor);
+
+	if (!(vcpu->arch.ctrl & 1))
+		mtspr(SPRN_CTRLT, mfspr(SPRN_CTRLF) & ~1);
+
+	mtspr(SPRN_DEC, vcpu->arch.dec_expires - mftb());
+
+	if (vcpu->arch.doorbell_request) {
+		vc->dpdes = 1;
+		smp_wmb();
+		vcpu->arch.doorbell_request = 0;
+	}
+
+	trap = kvmhv_load_hv_regs_and_go(vcpu, time_limit);
+
+	vcpu->arch.slb_max = 0;
+	dec = mfspr(SPRN_DEC);
+	tb = mftb();
+	vcpu->arch.dec_expires = dec + tb;
+	vcpu->cpu = -1;
+	vcpu->arch.thread_cpu = -1;
+	vcpu->arch.ctrl = mfspr(SPRN_CTRLF);
+
+	vcpu->arch.iamr = mfspr(SPRN_IAMR);
+	vcpu->arch.pspb = mfspr(SPRN_PSPB);
+	vcpu->arch.fscr = mfspr(SPRN_FSCR);
+	vcpu->arch.tar = mfspr(SPRN_TAR);
+	vcpu->arch.ebbhr = mfspr(SPRN_EBBHR);
+	vcpu->arch.ebbrr = mfspr(SPRN_EBBRR);
+	vcpu->arch.bescr = mfspr(SPRN_BESCR);
+	vcpu->arch.wort = mfspr(SPRN_WORT);
+	vcpu->arch.tid = mfspr(SPRN_TIDR);
+	vcpu->arch.amr = mfspr(SPRN_AMR);
+	vcpu->arch.uamor = mfspr(SPRN_UAMOR);
+	vcpu->arch.dscr = mfspr(SPRN_DSCR);
+
+	mtspr(SPRN_PSPB, 0);
+	mtspr(SPRN_WORT, 0);
+	mtspr(SPRN_AMR, 0);
+	mtspr(SPRN_UAMOR, 0);
+	mtspr(SPRN_DSCR, host_dscr);
+	mtspr(SPRN_TIDR, host_tidr);
+	mtspr(SPRN_IAMR, host_iamr);
+	mtspr(SPRN_PSPB, 0);
+
+	msr_check_and_set(MSR_FP | MSR_VEC | MSR_VSX);
+	store_fp_state(&vcpu->arch.fp);
+#ifdef CONFIG_ALTIVEC
+	store_vr_state(&vcpu->arch.vr);
+#endif
+
+	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);
+
+	save_pmu = 1;
+	if (vcpu->arch.vpa.pinned_addr) {
+		struct lppaca *lp = vcpu->arch.vpa.pinned_addr;
+		u32 yield_count = be32_to_cpu(lp->yield_count) + 1;
+		lp->yield_count = cpu_to_be32(yield_count);
+		vcpu->arch.vpa.dirty = 1;
+		save_pmu = lp->pmcregs_in_use;
+	}
+
+	kvmhv_save_guest_pmu(vcpu, save_pmu);
+
+	vc->entry_exit_map = 0x101;
+	vc->in_guest = 0;
+
+	mtspr(SPRN_DEC, local_paca->kvm_hstate.dec_expires - mftb());
+
+	kvmhv_load_host_pmu();
+
+	kvmppc_subcore_exit_guest();
+
+	return trap;
+}
+
+/*
  * Wait for some other vcpu thread to execute us, and
  * wake us up when we need to handle something in the host.
  */
@@ -3405,6 +3672,167 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 	return vcpu->arch.ret;
 }
 
+static int kvmhv_run_single_vcpu(struct kvm_run *kvm_run,
+				 struct kvm_vcpu *vcpu, u64 time_limit)
+{
+	int trap, r, pcpu, pcpu0;
+	int srcu_idx;
+	struct kvmppc_vcore *vc;
+	struct kvm *kvm = vcpu->kvm;
+
+	trace_kvmppc_run_vcpu_enter(vcpu);
+
+	kvm_run->exit_reason = 0;
+	vcpu->arch.ret = RESUME_GUEST;
+	vcpu->arch.trap = 0;
+
+	vc = vcpu->arch.vcore;
+	vcpu->arch.ceded = 0;
+	vcpu->arch.run_task = current;
+	vcpu->arch.kvm_run = kvm_run;
+	vcpu->arch.stolen_logged = vcore_stolen_time(vc, mftb());
+	vcpu->arch.state = KVMPPC_VCPU_RUNNABLE;
+	vcpu->arch.busy_preempt = TB_NIL;
+	vcpu->arch.last_inst = KVM_INST_FETCH_FAILED;
+	vc->runnable_threads[0] = vcpu;
+	vc->n_runnable = 1;
+	vc->runner = vcpu;
+
+	/* See if the MMU is ready to go */
+	if (!kvm->arch.mmu_ready) {
+		r = kvmhv_setup_mmu(vcpu);
+		if (r) {
+			kvm_run->exit_reason = KVM_EXIT_FAIL_ENTRY;
+			kvm_run->fail_entry.
+				hardware_entry_failure_reason = 0;
+			vcpu->arch.ret = r;
+			goto out;
+		}
+	}
+
+	if (need_resched())
+		cond_resched();
+
+	kvmppc_update_vpas(vcpu);
+
+	init_vcore_to_run(vc);
+	vc->preempt_tb = TB_NIL;
+
+	preempt_disable();
+	pcpu = smp_processor_id();
+	vc->pcpu = pcpu;
+	kvmppc_prepare_radix_vcpu(vcpu, pcpu);
+
+	local_irq_disable();
+	hard_irq_disable();
+	if (signal_pending(current))
+		goto sigpend;
+	if (lazy_irq_pending() || need_resched() || !kvm->arch.mmu_ready)
+		goto out;
+
+	kvmppc_core_prepare_to_enter(vcpu);
+
+	kvmppc_clear_host_core(pcpu);
+
+	local_paca->kvm_hstate.tid = 0;
+	local_paca->kvm_hstate.napping = 0;
+	local_paca->kvm_hstate.kvm_split_mode = NULL;
+	kvmppc_start_thread(vcpu, vc);
+	kvmppc_create_dtl_entry(vcpu, vc);
+	trace_kvm_guest_enter(vcpu);
+
+	vc->vcore_state = VCORE_RUNNING;
+	trace_kvmppc_run_core(vc, 0);
+
+	mtspr(SPRN_LPID, vc->kvm->arch.lpid);
+	isync();
+
+	/* See comment above in kvmppc_run_core() about this */
+	pcpu0 = pcpu;
+	if (cpu_has_feature(CPU_FTR_ARCH_300))
+		pcpu0 &= ~0x3UL;
+
+	if (cpumask_test_cpu(pcpu0, &kvm->arch.need_tlb_flush)) {
+		radix__local_flush_tlb_lpid_guest(kvm->arch.lpid);
+		/* Clear the bit after the TLB flush */
+		cpumask_clear_cpu(pcpu0, &kvm->arch.need_tlb_flush);
+	}
+
+	trace_hardirqs_on();
+	guest_enter_irqoff();
+
+	srcu_idx = srcu_read_lock(&kvm->srcu);
+
+	this_cpu_disable_ftrace();
+
+	trap = kvmhv_p9_guest_entry(vcpu, time_limit);
+	vcpu->arch.trap = trap;
+
+	this_cpu_enable_ftrace();
+
+	srcu_read_unlock(&kvm->srcu, srcu_idx);
+
+	mtspr(SPRN_LPID, kvm->arch.host_lpid);
+	isync();
+
+	trace_hardirqs_off();
+	set_irq_happened(trap);
+
+	kvmppc_set_host_core(pcpu);
+
+	local_irq_enable();
+	guest_exit();
+
+	cpumask_clear_cpu(pcpu, &kvm->arch.cpu_in_guest);
+
+	preempt_enable();
+
+	/* cancel pending decrementer exception if DEC is now positive */
+	if (get_tb() < vcpu->arch.dec_expires && kvmppc_core_pending_dec(vcpu))
+		kvmppc_core_dequeue_dec(vcpu);
+
+	trace_kvm_guest_exit(vcpu);
+	r = RESUME_GUEST;
+	if (trap)
+		r = kvmppc_handle_exit_hv(kvm_run, vcpu, current);
+	vcpu->arch.ret = r;
+
+	if (is_kvmppc_resume_guest(r) && vcpu->arch.ceded &&
+	    !kvmppc_vcpu_woken(vcpu)) {
+		kvmppc_set_timer(vcpu);
+		while (vcpu->arch.ceded && !kvmppc_vcpu_woken(vcpu)) {
+			if (signal_pending(current)) {
+				vcpu->stat.signal_exits++;
+				kvm_run->exit_reason = KVM_EXIT_INTR;
+				vcpu->arch.ret = -EINTR;
+				break;
+			}
+			spin_lock(&vc->lock);
+			kvmppc_vcore_blocked(vc);
+			spin_unlock(&vc->lock);
+		}
+	}
+	vcpu->arch.ceded = 0;
+
+	vc->vcore_state = VCORE_INACTIVE;
+	trace_kvmppc_run_core(vc, 1);
+
+ done:
+	kvmppc_remove_runnable(vc, vcpu);
+	trace_kvmppc_run_vcpu_exit(vcpu, kvm_run);
+
+	return vcpu->arch.ret;
+
+ sigpend:
+	vcpu->stat.signal_exits++;
+	kvm_run->exit_reason = KVM_EXIT_INTR;
+	vcpu->arch.ret = -EINTR;
+ out:
+	local_irq_enable();
+	preempt_enable();
+	goto done;
+}
+
 static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu)
 {
 	int r;
@@ -3480,7 +3908,10 @@ static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu)
 	vcpu->arch.state = KVMPPC_VCPU_BUSY_IN_HOST;
 
 	do {
-		r = kvmppc_run_vcpu(run, vcpu);
+		if (kvm->arch.threads_indep && kvm_is_radix(kvm))
+			r = kvmhv_run_single_vcpu(run, vcpu, ~(u64)0);
+		else
+			r = kvmppc_run_vcpu(run, vcpu);
 
 		if (run->exit_reason == KVM_EXIT_PAPR_HCALL &&
 		    !(vcpu->arch.shregs.msr & MSR_PR)) {