Subject: [PATCH v4 19/46] KVM: PPC: Book3S HV P9: Move radix MMU switching instructions together

From: Nicholas Piggin <[email-masked]>
Date: Tue, 23 Mar 2021 11:02:38 +1000

Switching the MMU from radix<->radix mode is tricky particularly as the
MMU can remain enabled and requires a certain sequence of SPR updates.
Move these together into their own functions.

This also includes the radix TLB check / flush because it's tied in to
MMU switching due to tlbiel getting LPID from LPIDR.

Reviewed-by: Alexey Kardashevskiy <[email-masked]>
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/kvm/book3s_hv.c | 66 +++++++++++++++++++++++-------------
 1 file changed, 43 insertions(+), 23 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 7bb4222729b0..b822c573dc08 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -3472,12 +3472,49 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
 	trace_kvmppc_run_core(vc, 1);
 }
 
+static void switch_mmu_to_guest_radix(struct kvm *kvm, struct kvm_vcpu *vcpu, u64 lpcr)
+{
+	struct kvmppc_vcore *vc = vcpu->arch.vcore;
+	struct kvm_nested_guest *nested = vcpu->arch.nested;
+	u32 lpid;
+
+	lpid = nested ? nested->shadow_lpid : kvm->arch.lpid;
+
+	/*
+	 * All the isync()s are overkill but trivially follow the ISA
+	 * requirements. Some can likely be replaced with justification
+	 * comment for why they are not needed.
+	 */
+	isync();
+	mtspr(SPRN_LPID, lpid);
+	isync();
+	mtspr(SPRN_LPCR, lpcr);
+	isync();
+	mtspr(SPRN_PID, vcpu->arch.pid);
+	isync();
+
+	/* TLBIEL must have LPIDR set, so set guest LPID before flushing. */
+	kvmppc_check_need_tlb_flush(kvm, vc->pcpu, nested);
+}
+
+static void switch_mmu_to_host_radix(struct kvm *kvm, u32 pid)
+{
+	isync();
+	mtspr(SPRN_PID, pid);
+	isync();
+	mtspr(SPRN_LPID, kvm->arch.host_lpid);
+	isync();
+	mtspr(SPRN_LPCR, kvm->arch.host_lpcr);
+	isync();
+}
+
 /*
  * Load up hypervisor-mode registers on P9.
  */
 static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 				     unsigned long lpcr)
 {
+	struct kvm *kvm = vcpu->kvm;
 	struct kvmppc_vcore *vc = vcpu->arch.vcore;
 	s64 hdec;
 	u64 tb, purr, spurr;
@@ -3500,12 +3537,12 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 	 * P8 and P9 suppress the HDEC exception when LPCR[HDICE] = 0,
 	 * so set HDICE before writing HDEC.
 	 */
-	mtspr(SPRN_LPCR, vcpu->kvm->arch.host_lpcr | LPCR_HDICE);
+	mtspr(SPRN_LPCR, kvm->arch.host_lpcr | LPCR_HDICE);
 	isync();
 
 	hdec = time_limit - mftb();
 	if (hdec < 0) {
-		mtspr(SPRN_LPCR, vcpu->kvm->arch.host_lpcr);
+		mtspr(SPRN_LPCR, kvm->arch.host_lpcr);
 		isync();
 		return BOOK3S_INTERRUPT_HV_DECREMENTER;
 	}
@@ -3540,7 +3577,6 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 	}
 	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));
@@ -3554,8 +3590,7 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 
 	mtspr(SPRN_AMOR, ~0UL);
 
-	mtspr(SPRN_LPCR, lpcr);
-	isync();
+	switch_mmu_to_guest_radix(kvm, vcpu, lpcr);
 
 	kvmppc_xive_push_vcpu(vcpu);
 
@@ -3594,7 +3629,6 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 		mtspr(SPRN_DAWR1, host_dawr1);
 		mtspr(SPRN_DAWRX1, host_dawrx1);
 	}
-	mtspr(SPRN_PID, host_pidr);
 
 	/*
 	 * Since this is radix, do a eieio; tlbsync; ptesync sequence in
@@ -3609,9 +3643,6 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 	if (cpu_has_feature(CPU_FTR_ARCH_31))
 		asm volatile(PPC_CP_ABORT);
 
-	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);
@@ -3628,7 +3659,8 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 	}
 
 	mtspr(SPRN_HDEC, 0x7fffffff);
-	mtspr(SPRN_LPCR, vcpu->kvm->arch.host_lpcr);
+
+	switch_mmu_to_host_radix(kvm, host_pidr);
 
 	return trap;
 }
@@ -4161,7 +4193,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
 {
 	struct kvm_run *run = vcpu->run;
 	int trap, r, pcpu;
-	int srcu_idx, lpid;
+	int srcu_idx;
 	struct kvmppc_vcore *vc;
 	struct kvm *kvm = vcpu->kvm;
 	struct kvm_nested_guest *nested = vcpu->arch.nested;
@@ -4235,13 +4267,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
 	vc->vcore_state = VCORE_RUNNING;
 	trace_kvmppc_run_core(vc, 0);
 
-	if (cpu_has_feature(CPU_FTR_HVMODE)) {
-		lpid = nested ? nested->shadow_lpid : kvm->arch.lpid;
-		mtspr(SPRN_LPID, lpid);
-		isync();
-		kvmppc_check_need_tlb_flush(kvm, pcpu, nested);
-	}
-
 	guest_enter_irqoff();
 
 	srcu_idx = srcu_read_lock(&kvm->srcu);
@@ -4260,11 +4285,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
 
 	srcu_read_unlock(&kvm->srcu, srcu_idx);
 
-	if (cpu_has_feature(CPU_FTR_HVMODE)) {
-		mtspr(SPRN_LPID, kvm->arch.host_lpid);
-		isync();
-	}
-
 	set_irq_happened(trap);
 
 	kvmppc_set_host_core(pcpu);
-- 
2.23.0