KVM: PPC: Book3S HV P9: implement hash host / hash guest support

Implement support for hash guests under hash host. This has to save and
restore the host SLB, and ensure that the MMU is off while switching
into the guest SLB.

POWER9 and later CPUs now always go via the P9 path. The "fast" guest
mode is now renamed to the P9 mode, which is consistent with its
functionality and the rest of the naming.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210528090752.3542186-32-npiggin@gmail.com

arch/powerpc/include/asm/kvm_asm.h

@@ -147,7 +147,7 @@
 #define KVM_GUEST_MODE_SKIP	2
 #define KVM_GUEST_MODE_GUEST_HV	3
 #define KVM_GUEST_MODE_HOST_HV	4
-#define KVM_GUEST_MODE_HV_FAST	5 /* ISA >= v3.0 host radix */
+#define KVM_GUEST_MODE_HV_P9	5 /* ISA >= v3.0 path */
 
 #define KVM_INST_FETCH_FAILED	-1
 

arch/powerpc/kvm/book3s_64_entry.S

@@ -36,7 +36,7 @@
 kvmppc_hcall:
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 	lbz	r10,HSTATE_IN_GUEST(r13)
-	cmpwi	r10,KVM_GUEST_MODE_HV_FAST
+	cmpwi	r10,KVM_GUEST_MODE_HV_P9
 	beq	kvmppc_p9_exit_hcall
 #endif
 	ld	r10,PACA_EXGEN+EX_R13(r13)
@@ -68,7 +68,7 @@ kvmppc_interrupt:
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 	std	r10,HSTATE_SCRATCH0(r13)
 	lbz	r10,HSTATE_IN_GUEST(r13)
-	cmpwi	r10,KVM_GUEST_MODE_HV_FAST
+	cmpwi	r10,KVM_GUEST_MODE_HV_P9
 	beq	kvmppc_p9_exit_interrupt
 	ld	r10,HSTATE_SCRATCH0(r13)
 #endif
@@ -183,8 +183,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 /*
  * void kvmppc_p9_enter_guest(struct vcpu *vcpu);
  *
- * Enter the guest on a ISAv3.0 or later system where we have exactly
+ * Enter the guest on a ISAv3.0 or later system.
- * one vcpu per vcore, and the host is radix.
  */
 .balign	IFETCH_ALIGN_BYTES
 _GLOBAL(kvmppc_p9_enter_guest)
@@ -284,7 +283,7 @@ kvmppc_p9_exit_hcall:
 .balign	IFETCH_ALIGN_BYTES
 kvmppc_p9_exit_interrupt:
 	/*
-	 * If set to KVM_GUEST_MODE_HV_FAST but we're still in the
+	 * If set to KVM_GUEST_MODE_HV_P9 but we're still in the
 	 * hypervisor, that means we can't return from the entry stack.
 	 */
 	rldicl. r10,r12,64-MSR_HV_LG,63
@@ -358,6 +357,12 @@ kvmppc_p9_exit_interrupt:
  * effort for a small bit of code. Lots of other things to do first.
  */
 kvmppc_p9_bad_interrupt:
+BEGIN_MMU_FTR_SECTION
+	/*
+	 * Hash host doesn't try to recover MMU (requires host SLB reload)
+	 */
+	b	.
+END_MMU_FTR_SECTION_IFCLR(MMU_FTR_TYPE_RADIX)
 	/*
 	 * Clean up guest registers to give host a chance to run.
 	 */

arch/powerpc/kvm/book3s_hv.c

@@ -4511,7 +4511,7 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu)
 	vcpu->arch.state = KVMPPC_VCPU_BUSY_IN_HOST;
 
 	do {
-		if (radix_enabled())
+		if (cpu_has_feature(CPU_FTR_ARCH_300))
 			r = kvmhv_run_single_vcpu(vcpu, ~(u64)0,
 						  vcpu->arch.vcore->lpcr);
 		else
@@ -5599,6 +5599,8 @@ static int kvmhv_enable_nested(struct kvm *kvm)
 		return -EPERM;
 	if (!cpu_has_feature(CPU_FTR_ARCH_300))
 		return -ENODEV;
+	if (!radix_enabled())
+		return -ENODEV;
 
 	/* kvm == NULL means the caller is testing if the capability exists */
 	if (kvm)

arch/powerpc/kvm/book3s_hv_p9_entry.c

@@ -130,7 +130,7 @@ static void switch_mmu_to_guest_hpt(struct kvm *kvm, struct kvm_vcpu *vcpu, u64
 	isync();
 }
 
-static void switch_mmu_to_host_radix(struct kvm *kvm, u32 pid)
+static void switch_mmu_to_host(struct kvm *kvm, u32 pid)
 {
 	isync();
 	mtspr(SPRN_PID, pid);
@@ -139,6 +139,22 @@ static void switch_mmu_to_host_radix(struct kvm *kvm, u32 pid)
 	isync();
 	mtspr(SPRN_LPCR, kvm->arch.host_lpcr);
 	isync();
+
+	if (!radix_enabled())
+		slb_restore_bolted_realmode();
+}
+
+static void save_clear_host_mmu(struct kvm *kvm)
+{
+	if (!radix_enabled()) {
+		/*
+		 * Hash host could save and restore host SLB entries to
+		 * reduce SLB fault overheads of VM exits, but for now the
+		 * existing code clears all entries and restores just the
+		 * bolted ones when switching back to host.
+		 */
+		slb_clear_invalidate_partition();
+	}
 }
 
 static void save_clear_guest_mmu(struct kvm *kvm, struct kvm_vcpu *vcpu)
@@ -271,16 +287,24 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
 
 	mtspr(SPRN_AMOR, ~0UL);
 
-	local_paca->kvm_hstate.in_guest = KVM_GUEST_MODE_HV_FAST;
+	local_paca->kvm_hstate.in_guest = KVM_GUEST_MODE_HV_P9;
+
+	/*
+	 * Hash host, hash guest, or radix guest with prefetch bug, all have
+	 * to disable the MMU before switching to guest MMU state.
+	 */
+	if (!radix_enabled() || !kvm_is_radix(kvm) ||
+			cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG))
+		__mtmsrd(msr & ~(MSR_IR|MSR_DR|MSR_RI), 0);
+
+	save_clear_host_mmu(kvm);
+
 	if (kvm_is_radix(kvm)) {
-		if (cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG))
-			__mtmsrd(msr & ~(MSR_IR|MSR_DR|MSR_RI), 0);
 		switch_mmu_to_guest_radix(kvm, vcpu, lpcr);
 		if (!cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG))
 			__mtmsrd(0, 1); /* clear RI */
 
 	} else {
-		__mtmsrd(msr & ~(MSR_IR|MSR_DR|MSR_RI), 0);
 		switch_mmu_to_guest_hpt(kvm, vcpu, lpcr);
 	}
 
@@ -468,7 +492,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
 	mtspr(SPRN_HDEC, 0x7fffffff);
 
 	save_clear_guest_mmu(kvm, vcpu);
-	switch_mmu_to_host_radix(kvm, host_pidr);
+	switch_mmu_to_host(kvm, host_pidr);
 	local_paca->kvm_hstate.in_guest = KVM_GUEST_MODE_NONE;
 
 	/*