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

1 files changed, 30 insertions, 6 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c b/arch/powerpc/kvm/book3s_hv_p9_entry.c
index 4460f1c23a9d..83f592eadcd2 100644
--- a/arch/powerpc/kvm/book3s_hv_p9_entry.c
+++ b/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;
 
 	/*