kvm: x86/mmu: Init / Uninit the TDP MMU

The TDP MMU offers an alternative mode of operation to the x86 shadow
paging based MMU, optimized for running an L1 guest with TDP. The TDP MMU
will require new fields that need to be initialized and torn down. Add
hooks into the existing KVM MMU initialization process to do that
initialization / cleanup. Currently the initialization and cleanup
fucntions do not do very much, however more operations will be added in
future patches.

Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.

This series can be viewed in Gerrit at:
	https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-4-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -995,6 +995,15 @@ struct kvm_arch {
 
 	struct kvm_pmu_event_filter *pmu_event_filter;
 	struct task_struct *nx_lpage_recovery_thread;
+
+	/*
+	 * Whether the TDP MMU is enabled for this VM. This contains a
+	 * snapshot of the TDP MMU module parameter from when the VM was
+	 * created and remains unchanged for the life of the VM. If this is
+	 * true, TDP MMU handler functions will run for various MMU
+	 * operations.
+	 */
+	bool tdp_mmu_enabled;
 };
 
 struct kvm_vm_stat {

arch/x86/kvm/Makefile

@@ -16,7 +16,7 @@ kvm-$(CONFIG_KVM_ASYNC_PF)	+= $(KVM)/async_pf.o
 kvm-y			+= x86.o emulate.o i8259.o irq.o lapic.o \
 			   i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \
 			   hyperv.o debugfs.o mmu/mmu.o mmu/page_track.o \
-			   mmu/spte.o mmu/tdp_iter.o
+			   mmu/spte.o mmu/tdp_iter.o mmu/tdp_mmu.o
 
 kvm-intel-y		+= vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \
 			   vmx/evmcs.o vmx/nested.o vmx/posted_intr.o

arch/x86/kvm/mmu/mmu.c

@@ -19,6 +19,7 @@
 #include "ioapic.h"
 #include "mmu.h"
 #include "mmu_internal.h"
+#include "tdp_mmu.h"
 #include "x86.h"
 #include "kvm_cache_regs.h"
 #include "kvm_emulate.h"
@@ -5377,6 +5378,8 @@ void kvm_mmu_init_vm(struct kvm *kvm)
 {
 	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
 
+	kvm_mmu_init_tdp_mmu(kvm);
+
 	node->track_write = kvm_mmu_pte_write;
 	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
 	kvm_page_track_register_notifier(kvm, node);
@@ -5387,6 +5390,8 @@ void kvm_mmu_uninit_vm(struct kvm *kvm)
 	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
 
 	kvm_page_track_unregister_notifier(kvm, node);
+
+	kvm_mmu_uninit_tdp_mmu(kvm);
 }
 
 void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)

arch/x86/kvm/mmu/tdp_mmu.c

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "tdp_mmu.h"
+
+static bool __read_mostly tdp_mmu_enabled = false;
+
+static bool is_tdp_mmu_enabled(void)
+{
+#ifdef CONFIG_X86_64
+	return tdp_enabled && READ_ONCE(tdp_mmu_enabled);
+#else
+	return false;
+#endif /* CONFIG_X86_64 */
+}
+
+/* Initializes the TDP MMU for the VM, if enabled. */
+void kvm_mmu_init_tdp_mmu(struct kvm *kvm)
+{
+	if (!is_tdp_mmu_enabled())
+		return;
+
+	/* This should not be changed for the lifetime of the VM. */
+	kvm->arch.tdp_mmu_enabled = true;
+}
+
+void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
+{
+	if (!kvm->arch.tdp_mmu_enabled)
+		return;
+}

arch/x86/kvm/mmu/tdp_mmu.h

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef __KVM_X86_MMU_TDP_MMU_H
+#define __KVM_X86_MMU_TDP_MMU_H
+
+#include <linux/kvm_host.h>
+
+void kvm_mmu_init_tdp_mmu(struct kvm *kvm);
+void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm);
+#endif /* __KVM_X86_MMU_TDP_MMU_H */