Merge tag 'kvm-x86-mmu-6.17' of https://github.com/kvm-x86/linux into HEAD

KVM x86 MMU changes for 6.17

 - Exempt nested EPT from the the !USER + CR0.WP logic, as EPT doesn't interact
   with CR0.WP.

 - Move the TDX hardware setup code to tdx.c to better co-locate TDX code
   and eliminate a few global symbols.

 - Dynamically allocation the shadow MMU's hashed page list, and defer
   allocating the hashed list until it's actually needed (the TDP MMU doesn't
   use the list).

Author: bonzini

arch/x86/include/asm/kvm_host.h

@@ -1358,7 +1358,7 @@ struct kvm_arch {
 	bool has_private_mem;
 	bool has_protected_state;
 	bool pre_fault_allowed;
-	struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
+	struct hlist_head *mmu_page_hash;
 	struct list_head active_mmu_pages;
 	/*
 	 * A list of kvm_mmu_page structs that, if zapped, could possibly be
@@ -1985,7 +1985,7 @@ void kvm_x86_vendor_exit(void);
 #define __KVM_HAVE_ARCH_VM_ALLOC
 static inline struct kvm *kvm_arch_alloc_vm(void)
 {
-	return __vmalloc(kvm_x86_ops.vm_size, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+	return kvzalloc(kvm_x86_ops.vm_size, GFP_KERNEL_ACCOUNT);
 }
 
 #define __KVM_HAVE_ARCH_VM_FREE
@@ -2030,7 +2030,7 @@ void kvm_mmu_vendor_module_exit(void);
 
 void kvm_mmu_destroy(struct kvm_vcpu *vcpu);
 int kvm_mmu_create(struct kvm_vcpu *vcpu);
-void kvm_mmu_init_vm(struct kvm *kvm);
+int kvm_mmu_init_vm(struct kvm *kvm);
 void kvm_mmu_uninit_vm(struct kvm *kvm);
 
 void kvm_mmu_init_memslot_memory_attributes(struct kvm *kvm,

arch/x86/kvm/mmu/mmu.c

@@ -1983,14 +1983,35 @@ static bool sp_has_gptes(struct kvm_mmu_page *sp)
 	return true;
 }
 
+static __ro_after_init HLIST_HEAD(empty_page_hash);
+
+static struct hlist_head *kvm_get_mmu_page_hash(struct kvm *kvm, gfn_t gfn)
+{
+	/*
+	 * Ensure the load of the hash table pointer itself is ordered before
+	 * loads to walk the table.  The pointer is set at runtime outside of
+	 * mmu_lock when the TDP MMU is enabled, i.e. when the hash table of
+	 * shadow pages becomes necessary only when KVM needs to shadow L1's
+	 * TDP for an L2 guest.  Pairs with the smp_store_release() in
+	 * kvm_mmu_alloc_page_hash().
+	 */
+	struct hlist_head *page_hash = smp_load_acquire(&kvm->arch.mmu_page_hash);
+
+	lockdep_assert_held(&kvm->mmu_lock);
+
+	if (!page_hash)
+		return &empty_page_hash;
+
+	return &page_hash[kvm_page_table_hashfn(gfn)];
+}
+
 #define for_each_valid_sp(_kvm, _sp, _list)				\
 	hlist_for_each_entry(_sp, _list, hash_link)			\
 		if (is_obsolete_sp((_kvm), (_sp))) {			\
 		} else
 
 #define for_each_gfn_valid_sp_with_gptes(_kvm, _sp, _gfn)		\
-	for_each_valid_sp(_kvm, _sp,					\
-	  &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)])	\
+	for_each_valid_sp(_kvm, _sp, kvm_get_mmu_page_hash(_kvm, _gfn))	\
 		if ((_sp)->gfn != (_gfn) || !sp_has_gptes(_sp)) {} else
 
 static bool kvm_sync_page_check(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
@@ -2358,6 +2379,12 @@ static struct kvm_mmu_page *__kvm_mmu_get_shadow_page(struct kvm *kvm,
 	struct kvm_mmu_page *sp;
 	bool created = false;
 
+	/*
+	 * No need for memory barriers, unlike in kvm_get_mmu_page_hash(), as
+	 * mmu_page_hash must be set prior to creating the first shadow root,
+	 * i.e. reaching this point is fully serialized by slots_arch_lock.
+	 */
+	BUG_ON(!kvm->arch.mmu_page_hash);
 	sp_list = &kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)];
 
 	sp = kvm_mmu_find_shadow_page(kvm, vcpu, gfn, sp_list, role);
@@ -3882,6 +3909,28 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
 	return r;
 }
 
+static int kvm_mmu_alloc_page_hash(struct kvm *kvm)
+{
+	struct hlist_head *h;
+
+	if (kvm->arch.mmu_page_hash)
+		return 0;
+
+	h = kvcalloc(KVM_NUM_MMU_PAGES, sizeof(*h), GFP_KERNEL_ACCOUNT);
+	if (!h)
+		return -ENOMEM;
+
+	/*
+	 * Ensure the hash table pointer is set only after all stores to zero
+	 * the memory are retired.  Pairs with the smp_load_acquire() in
+	 * kvm_get_mmu_page_hash().  Note, mmu_lock must be held for write to
+	 * add (or remove) shadow pages, and so readers are guaranteed to see
+	 * an empty list for their current mmu_lock critical section.
+	 */
+	smp_store_release(&kvm->arch.mmu_page_hash, h);
+	return 0;
+}
+
 static int mmu_first_shadow_root_alloc(struct kvm *kvm)
 {
 	struct kvm_memslots *slots;
@@ -3901,9 +3950,13 @@ static int mmu_first_shadow_root_alloc(struct kvm *kvm)
 	if (kvm_shadow_root_allocated(kvm))
 		goto out_unlock;
 
+	r = kvm_mmu_alloc_page_hash(kvm);
+	if (r)
+		goto out_unlock;
+
 	/*
-	 * Check if anything actually needs to be allocated, e.g. all metadata
-	 * will be allocated upfront if TDP is disabled.
+	 * Check if memslot metadata actually needs to be allocated, e.g. all
+	 * metadata will be allocated upfront if TDP is disabled.
 	 */
 	if (kvm_memslots_have_rmaps(kvm) &&
 	    kvm_page_track_write_tracking_enabled(kvm))
@@ -6682,15 +6735,22 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
 		kvm_tdp_mmu_zap_invalidated_roots(kvm, true);
 }
 
-void kvm_mmu_init_vm(struct kvm *kvm)
+int kvm_mmu_init_vm(struct kvm *kvm)
 {
+	int r;
+
 	kvm->arch.shadow_mmio_value = shadow_mmio_value;
 	INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
 	INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages);
 	spin_lock_init(&kvm->arch.mmu_unsync_pages_lock);
 
-	if (tdp_mmu_enabled)
+	if (tdp_mmu_enabled) {
 		kvm_mmu_init_tdp_mmu(kvm);
+	} else {
+		r = kvm_mmu_alloc_page_hash(kvm);
+		if (r)
+			return r;
+	}
 
 	kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
 	kvm->arch.split_page_header_cache.gfp_zero = __GFP_ZERO;
@@ -6699,6 +6759,7 @@ void kvm_mmu_init_vm(struct kvm *kvm)
 
 	kvm->arch.split_desc_cache.kmem_cache = pte_list_desc_cache;
 	kvm->arch.split_desc_cache.gfp_zero = __GFP_ZERO;
+	return 0;
 }
 
 static void mmu_free_vm_memory_caches(struct kvm *kvm)
@@ -6710,6 +6771,8 @@ static void mmu_free_vm_memory_caches(struct kvm *kvm)
 
 void kvm_mmu_uninit_vm(struct kvm *kvm)
 {
+	kvfree(kvm->arch.mmu_page_hash);
+
 	if (tdp_mmu_enabled)
 		kvm_mmu_uninit_tdp_mmu(kvm);
 

arch/x86/kvm/mmu/paging_tmpl.h

@@ -804,9 +804,12 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 	if (r != RET_PF_CONTINUE)
 		return r;
 
+#if PTTYPE != PTTYPE_EPT
 	/*
-	 * Do not change pte_access if the pfn is a mmio page, otherwise
-	 * we will cache the incorrect access into mmio spte.
+	 * Treat the guest PTE protections as writable, supervisor-only if this
+	 * is a supervisor write fault and CR0.WP=0 (supervisor accesses ignore
+	 * PTE.W if CR0.WP=0).  Don't change the access type for emulated MMIO,
+	 * otherwise KVM will cache incorrect access information in the SPTE.
 	 */
 	if (fault->write && !(walker.pte_access & ACC_WRITE_MASK) &&
 	    !is_cr0_wp(vcpu->arch.mmu) && !fault->user && fault->slot) {
@@ -822,6 +825,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 		if (is_cr4_smep(vcpu->arch.mmu))
 			walker.pte_access &= ~ACC_EXEC_MASK;
 	}
+#endif
 
 	r = RET_PF_RETRY;
 	write_lock(&vcpu->kvm->mmu_lock);

arch/x86/kvm/svm/svm.c

@@ -5494,6 +5494,8 @@ static int __init svm_init(void)
 {
 	int r;
 
+	KVM_SANITY_CHECK_VM_STRUCT_SIZE(kvm_svm);
+
 	__unused_size_checks();
 
 	if (!kvm_is_svm_supported())

arch/x86/kvm/vmx/main.c

@@ -29,40 +29,8 @@ static __init int vt_hardware_setup(void)
 	if (ret)
 		return ret;
 
-	/*
-	 * Update vt_x86_ops::vm_size here so it is ready before
-	 * kvm_ops_update() is called in kvm_x86_vendor_init().
-	 *
-	 * Note, the actual bringing up of TDX must be done after
-	 * kvm_ops_update() because enabling TDX requires enabling
-	 * hardware virtualization first, i.e., all online CPUs must
-	 * be in post-VMXON state.  This means the @vm_size here
-	 * may be updated to TDX's size but TDX may fail to enable
-	 * at later time.
-	 *
-	 * The VMX/VT code could update kvm_x86_ops::vm_size again
-	 * after bringing up TDX, but this would require exporting
-	 * either kvm_x86_ops or kvm_ops_update() from the base KVM
-	 * module, which looks overkill.  Anyway, the worst case here
-	 * is KVM may allocate couple of more bytes than needed for
-	 * each VM.
-	 */
-	if (enable_tdx) {
-		vt_x86_ops.vm_size = max_t(unsigned int, vt_x86_ops.vm_size,
-				sizeof(struct kvm_tdx));
-		/*
-		 * Note, TDX may fail to initialize in a later time in
-		 * vt_init(), in which case it is not necessary to setup
-		 * those callbacks.  But making them valid here even
-		 * when TDX fails to init later is fine because those
-		 * callbacks won't be called if the VM isn't TDX guest.
-		 */
-		vt_x86_ops.link_external_spt = tdx_sept_link_private_spt;
-		vt_x86_ops.set_external_spte = tdx_sept_set_private_spte;
-		vt_x86_ops.free_external_spt = tdx_sept_free_private_spt;
-		vt_x86_ops.remove_external_spte = tdx_sept_remove_private_spte;
-		vt_x86_ops.protected_apic_has_interrupt = tdx_protected_apic_has_interrupt;
-	}
+	if (enable_tdx)
+		tdx_hardware_setup();
 
 	return 0;
 }

arch/x86/kvm/vmx/tdx.c

@@ -743,7 +743,7 @@ bool tdx_interrupt_allowed(struct kvm_vcpu *vcpu)
 	       !to_tdx(vcpu)->vp_enter_args.r12;
 }
 
-bool tdx_protected_apic_has_interrupt(struct kvm_vcpu *vcpu)
+static bool tdx_protected_apic_has_interrupt(struct kvm_vcpu *vcpu)
 {
 	u64 vcpu_state_details;
 
@@ -1638,8 +1638,8 @@ static int tdx_mem_page_record_premap_cnt(struct kvm *kvm, gfn_t gfn,
 	return 0;
 }
 
-int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
-			      enum pg_level level, kvm_pfn_t pfn)
+static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
+				     enum pg_level level, kvm_pfn_t pfn)
 {
 	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
 	struct page *page = pfn_to_page(pfn);
@@ -1719,8 +1719,8 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
 	return 0;
 }
 
-int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn,
-			      enum pg_level level, void *private_spt)
+static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn,
+				     enum pg_level level, void *private_spt)
 {
 	int tdx_level = pg_level_to_tdx_sept_level(level);
 	gpa_t gpa = gfn_to_gpa(gfn);
@@ -1855,8 +1855,8 @@ static void tdx_track(struct kvm *kvm)
 	kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE);
 }
 
-int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn,
-			      enum pg_level level, void *private_spt)
+static int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn,
+				     enum pg_level level, void *private_spt)
 {
 	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
 
@@ -1878,8 +1878,8 @@ int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn,
 	return tdx_reclaim_page(virt_to_page(private_spt));
 }
 
-int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
-				 enum pg_level level, kvm_pfn_t pfn)
+static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
+					enum pg_level level, kvm_pfn_t pfn)
 {
 	struct page *page = pfn_to_page(pfn);
 	int ret;
@@ -3603,10 +3603,14 @@ int __init tdx_bringup(void)
 	r = __tdx_bringup();
 	if (r) {
 		/*
-		 * Disable TDX only but don't fail to load module if
-		 * the TDX module could not be loaded.  No need to print
-		 * message saying "module is not loaded" because it was
-		 * printed when the first SEAMCALL failed.
+		 * Disable TDX only but don't fail to load module if the TDX
+		 * module could not be loaded.  No need to print message saying
+		 * "module is not loaded" because it was printed when the first
+		 * SEAMCALL failed.  Don't bother unwinding the S-EPT hooks or
+		 * vm_size, as kvm_x86_ops have already been finalized (and are
+		 * intentionally not exported).  The S-EPT code is unreachable,
+		 * and allocating a few more bytes per VM in a should-be-rare
+		 * failure scenario is a non-issue.
 		 */
 		if (r == -ENODEV)
 			goto success_disable_tdx;
@@ -3620,3 +3624,20 @@ int __init tdx_bringup(void)
 	enable_tdx = 0;
 	return 0;
 }
+
+void __init tdx_hardware_setup(void)
+{
+	KVM_SANITY_CHECK_VM_STRUCT_SIZE(kvm_tdx);
+
+	/*
+	 * Note, if the TDX module can't be loaded, KVM TDX support will be
+	 * disabled but KVM will continue loading (see tdx_bringup()).
+	 */
+	vt_x86_ops.vm_size = max_t(unsigned int, vt_x86_ops.vm_size, sizeof(struct kvm_tdx));
+
+	vt_x86_ops.link_external_spt = tdx_sept_link_private_spt;
+	vt_x86_ops.set_external_spte = tdx_sept_set_private_spte;
+	vt_x86_ops.free_external_spt = tdx_sept_free_private_spt;
+	vt_x86_ops.remove_external_spte = tdx_sept_remove_private_spte;
+	vt_x86_ops.protected_apic_has_interrupt = tdx_protected_apic_has_interrupt;
+}

arch/x86/kvm/vmx/tdx.h

@@ -8,6 +8,7 @@
 #ifdef CONFIG_KVM_INTEL_TDX
 #include "common.h"
 
+void tdx_hardware_setup(void);
 int tdx_bringup(void);
 void tdx_cleanup(void);
 

arch/x86/kvm/vmx/vmx.c

@@ -8552,6 +8552,8 @@ int __init vmx_init(void)
 {
 	int r, cpu;
 
+	KVM_SANITY_CHECK_VM_STRUCT_SIZE(kvm_vmx);
+
 	if (!kvm_is_vmx_supported())
 		return -EOPNOTSUPP;
 

arch/x86/kvm/vmx/x86_ops.h

@@ -136,7 +136,6 @@ int tdx_vcpu_pre_run(struct kvm_vcpu *vcpu);
 fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags);
 void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu);
 void tdx_vcpu_put(struct kvm_vcpu *vcpu);
-bool tdx_protected_apic_has_interrupt(struct kvm_vcpu *vcpu);
 int tdx_handle_exit(struct kvm_vcpu *vcpu,
 		enum exit_fastpath_completion fastpath);
 
@@ -151,15 +150,6 @@ int tdx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr);
 
 int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp);
 
-int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn,
-			      enum pg_level level, void *private_spt);
-int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn,
-			      enum pg_level level, void *private_spt);
-int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
-			      enum pg_level level, kvm_pfn_t pfn);
-int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
-				 enum pg_level level, kvm_pfn_t pfn);
-
 void tdx_flush_tlb_current(struct kvm_vcpu *vcpu);
 void tdx_flush_tlb_all(struct kvm_vcpu *vcpu);
 void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int root_level);

arch/x86/kvm/x86.c

@@ -12699,7 +12699,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	if (ret)
 		goto out;
 
-	kvm_mmu_init_vm(kvm);
+	ret = kvm_mmu_init_vm(kvm);
+	if (ret)
+		goto out_cleanup_page_track;
 
 	ret = kvm_x86_call(vm_init)(kvm);
 	if (ret)
@@ -12745,6 +12747,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 out_uninit_mmu:
 	kvm_mmu_uninit_vm(kvm);
+out_cleanup_page_track:
 	kvm_page_track_cleanup(kvm);
 out:
 	return ret;