Re: [PATCH v2 13/37] KVM: PPC: Book3S HV P9: Move radix MMU switching instructions together

Excerpts from Fabiano Rosas's message of February 27, 2021 1:56 am:

Nicholas Piggin [off-list ref] writes:

quoted

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.

(XXX: isync / hwsync synchronisation TBD)

I see bot mtlpidr and mtlpcr requiring a CSI in the ISA. Do you say we
might need more than an isync?

We might need a CSI before it, we might also need a hwsync before it. I
don't know whether we need isyncs between any of them (I don't think we
should because they're all mtsprs).

Regardless, I'd expect that to be separate from the refactoring here,
so:

Reviewed-by: Fabiano Rosas <redacted>

Thanks,
Nick

quoted

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kvm/book3s_hv.c | 55 +++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 895090636295..23d6dc04b0e9 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c

@@ -3440,12 +3440,38 @@ 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;
+
+	mtspr(SPRN_LPID, lpid);
+	mtspr(SPRN_LPCR, lpcr);
+	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)
+{
+	mtspr(SPRN_PID, pid);
+	mtspr(SPRN_LPID, kvm->arch.host_lpid);
+	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;

@@ -3468,12 +3494,12 @@ 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;
 	}

@@ -3508,7 +3534,6 @@ 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));

@@ -3522,8 +3547,7 @@ 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);

@@ -3562,7 +3586,6 @@ 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

@@ -3577,9 +3600,6 @@ 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);

@@ -3596,7 +3616,8 @@ 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;
 }

@@ -4130,7 +4151,7 @@ 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;

@@ -4204,13 +4225,6 @@ 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);

@@ -4229,11 +4243,6 @@ 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);