KVM: Remove memory alias support

As advertised in feature-removal-schedule.txt.  Equivalent support is provided
by overlapping memory regions.

Signed-off-by: Avi Kivity <avi@redhat.com>

Documentation/feature-removal-schedule.txt

@@ -538,17 +538,6 @@ Who:	Jan Kiszka <jan.kiszka@web.de>
 
 ----------------------------
 
-What:	KVM memory aliases support
-When:	July 2010
-Why:	Memory aliasing support is used for speeding up guest vga access
-	through the vga windows.
-
-	Modern userspace no longer uses this feature, so it's just bitrotted
-	code and can be removed with no impact.
-Who:	Avi Kivity <avi@redhat.com>
-
-----------------------------
-
 What:	xtime, wall_to_monotonic
 When:	2.6.36+
 Files:	kernel/time/timekeeping.c include/linux/time.h

Documentation/kvm/api.txt

@@ -226,17 +226,7 @@ Type: vm ioctl
 Parameters: struct kvm_memory_alias (in)
 Returns: 0 (success), -1 (error)
 
-struct kvm_memory_alias {
-	__u32 slot;  /* this has a different namespace than memory slots */
-	__u32 flags;
-	__u64 guest_phys_addr;
-	__u64 memory_size;
-	__u64 target_phys_addr;
-};
-
-Defines a guest physical address space region as an alias to another
-region.  Useful for aliased address, for example the VGA low memory
-window. Should not be used with userspace memory.
+This ioctl is obsolete and has been removed.
 
 4.9 KVM_RUN
 

arch/ia64/kvm/kvm-ia64.c

@@ -1946,11 +1946,6 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 	return vcpu->arch.timer_fired;
 }
 
-gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
-{
-	return gfn;
-}
-
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 {
 	return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE) ||

arch/powerpc/kvm/powerpc.c

@@ -36,11 +36,6 @@
 #define CREATE_TRACE_POINTS
 #include "trace.h"
 
-gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
-{
-	return gfn;
-}
-
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 {
 	return !(v->arch.msr & MSR_WE) || !!(v->arch.pending_exceptions);

arch/s390/kvm/kvm-s390.c

@@ -723,11 +723,6 @@ void kvm_arch_flush_shadow(struct kvm *kvm)
 {
 }
 
-gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
-{
-	return gfn;
-}
-
 static int __init kvm_s390_init(void)
 {
 	int ret;

arch/x86/include/asm/kvm_host.h

@@ -69,8 +69,6 @@
 
 #define IOPL_SHIFT 12
 
-#define KVM_ALIAS_SLOTS 4
-
 #define KVM_PERMILLE_MMU_PAGES 20
 #define KVM_MIN_ALLOC_MMU_PAGES 64
 #define KVM_MMU_HASH_SHIFT 10
@@ -362,24 +360,7 @@ struct kvm_vcpu_arch {
 	u64 hv_vapic;
 };
 
-struct kvm_mem_alias {
-	gfn_t base_gfn;
-	unsigned long npages;
-	gfn_t target_gfn;
-#define KVM_ALIAS_INVALID     1UL
-	unsigned long flags;
-};
-
-#define KVM_ARCH_HAS_UNALIAS_INSTANTIATION
-
-struct kvm_mem_aliases {
-	struct kvm_mem_alias aliases[KVM_ALIAS_SLOTS];
-	int naliases;
-};
-
 struct kvm_arch {
-	struct kvm_mem_aliases *aliases;
-
 	unsigned int n_free_mmu_pages;
 	unsigned int n_requested_mmu_pages;
 	unsigned int n_alloc_mmu_pages;
@@ -655,8 +636,6 @@ void kvm_disable_tdp(void);
 int complete_pio(struct kvm_vcpu *vcpu);
 bool kvm_check_iopl(struct kvm_vcpu *vcpu);
 
-struct kvm_memory_slot *gfn_to_memslot_unaliased(struct kvm *kvm, gfn_t gfn);
-
 static inline struct kvm_mmu_page *page_header(hpa_t shadow_page)
 {
 	struct page *page = pfn_to_page(shadow_page >> PAGE_SHIFT);

arch/x86/kvm/mmu.c

@@ -434,9 +434,7 @@ static void account_shadowed(struct kvm *kvm, gfn_t gfn)
 	int *write_count;
 	int i;
 
-	gfn = unalias_gfn(kvm, gfn);
-
-	slot = gfn_to_memslot_unaliased(kvm, gfn);
+	slot = gfn_to_memslot(kvm, gfn);
 	for (i = PT_DIRECTORY_LEVEL;
 	     i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
 		write_count   = slot_largepage_idx(gfn, slot, i);
@@ -450,8 +448,7 @@ static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
 	int *write_count;
 	int i;
 
-	gfn = unalias_gfn(kvm, gfn);
-	slot = gfn_to_memslot_unaliased(kvm, gfn);
+	slot = gfn_to_memslot(kvm, gfn);
 	for (i = PT_DIRECTORY_LEVEL;
 	     i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
 		write_count   = slot_largepage_idx(gfn, slot, i);
@@ -467,8 +464,7 @@ static int has_wrprotected_page(struct kvm *kvm,
 	struct kvm_memory_slot *slot;
 	int *largepage_idx;
 
-	gfn = unalias_gfn(kvm, gfn);
-	slot = gfn_to_memslot_unaliased(kvm, gfn);
+	slot = gfn_to_memslot(kvm, gfn);
 	if (slot) {
 		largepage_idx = slot_largepage_idx(gfn, slot, level);
 		return *largepage_idx;
@@ -521,7 +517,6 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn)
 
 /*
  * Take gfn and return the reverse mapping to it.
- * Note: gfn must be unaliased before this function get called
  */
 
 static unsigned long *gfn_to_rmap(struct kvm *kvm, gfn_t gfn, int level)
@@ -561,7 +556,6 @@ static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
 
 	if (!is_rmap_spte(*spte))
 		return count;
-	gfn = unalias_gfn(vcpu->kvm, gfn);
 	sp = page_header(__pa(spte));
 	kvm_mmu_page_set_gfn(sp, spte - sp->spt, gfn);
 	rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);
@@ -698,7 +692,6 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
 	u64 *spte;
 	int i, write_protected = 0;
 
-	gfn = unalias_gfn(kvm, gfn);
 	rmapp = gfn_to_rmap(kvm, gfn, PT_PAGE_TABLE_LEVEL);
 
 	spte = rmap_next(kvm, rmapp, NULL);
@@ -885,7 +878,6 @@ static void rmap_recycle(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
 
 	sp = page_header(__pa(spte));
 
-	gfn = unalias_gfn(vcpu->kvm, gfn);
 	rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);
 
 	kvm_unmap_rmapp(vcpu->kvm, rmapp, 0);
@@ -3510,8 +3502,7 @@ static void audit_write_protection(struct kvm_vcpu *vcpu)
 		if (sp->unsync)
 			continue;
 
-		gfn = unalias_gfn(vcpu->kvm, sp->gfn);
-		slot = gfn_to_memslot_unaliased(vcpu->kvm, sp->gfn);
+		slot = gfn_to_memslot(vcpu->kvm, sp->gfn);
 		rmapp = &slot->rmap[gfn - slot->base_gfn];
 
 		spte = rmap_next(vcpu->kvm, rmapp, NULL);

arch/x86/kvm/paging_tmpl.h

@@ -576,7 +576,6 @@ static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
  * Using the cached information from sp->gfns is safe because:
  * - The spte has a reference to the struct page, so the pfn for a given gfn
  *   can't change unless all sptes pointing to it are nuked first.
- * - Alias changes zap the entire shadow cache.
  */
 static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 			    bool clear_unsync)
@@ -611,7 +610,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 			return -EINVAL;
 
 		gfn = gpte_to_gfn(gpte);
-		if (unalias_gfn(vcpu->kvm, gfn) != sp->gfns[i] ||
+		if (gfn != sp->gfns[i] ||
 		      !is_present_gpte(gpte) || !(gpte & PT_ACCESSED_MASK)) {
 			u64 nonpresent;
 

arch/x86/kvm/x86.c

@@ -2740,115 +2740,6 @@ static int kvm_vm_ioctl_get_nr_mmu_pages(struct kvm *kvm)
 	return kvm->arch.n_alloc_mmu_pages;
 }
 
-gfn_t unalias_gfn_instantiation(struct kvm *kvm, gfn_t gfn)
-{
-	int i;
-	struct kvm_mem_alias *alias;
-	struct kvm_mem_aliases *aliases;
-
-	aliases = kvm_aliases(kvm);
-
-	for (i = 0; i < aliases->naliases; ++i) {
-		alias = &aliases->aliases[i];
-		if (alias->flags & KVM_ALIAS_INVALID)
-			continue;
-		if (gfn >= alias->base_gfn
-		    && gfn < alias->base_gfn + alias->npages)
-			return alias->target_gfn + gfn - alias->base_gfn;
-	}
-	return gfn;
-}
-
-gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
-{
-	int i;
-	struct kvm_mem_alias *alias;
-	struct kvm_mem_aliases *aliases;
-
-	aliases = kvm_aliases(kvm);
-
-	for (i = 0; i < aliases->naliases; ++i) {
-		alias = &aliases->aliases[i];
-		if (gfn >= alias->base_gfn
-		    && gfn < alias->base_gfn + alias->npages)
-			return alias->target_gfn + gfn - alias->base_gfn;
-	}
-	return gfn;
-}
-
-/*
- * Set a new alias region.  Aliases map a portion of physical memory into
- * another portion.  This is useful for memory windows, for example the PC
- * VGA region.
- */
-static int kvm_vm_ioctl_set_memory_alias(struct kvm *kvm,
-					 struct kvm_memory_alias *alias)
-{
-	int r, n;
-	struct kvm_mem_alias *p;
-	struct kvm_mem_aliases *aliases, *old_aliases;
-
-	r = -EINVAL;
-	/* General sanity checks */
-	if (alias->memory_size & (PAGE_SIZE - 1))
-		goto out;
-	if (alias->guest_phys_addr & (PAGE_SIZE - 1))
-		goto out;
-	if (alias->slot >= KVM_ALIAS_SLOTS)
-		goto out;
-	if (alias->guest_phys_addr + alias->memory_size
-	    < alias->guest_phys_addr)
-		goto out;
-	if (alias->target_phys_addr + alias->memory_size
-	    < alias->target_phys_addr)
-		goto out;
-
-	r = -ENOMEM;
-	aliases = kzalloc(sizeof(struct kvm_mem_aliases), GFP_KERNEL);
-	if (!aliases)
-		goto out;
-
-	mutex_lock(&kvm->slots_lock);
-
-	/* invalidate any gfn reference in case of deletion/shrinking */
-	memcpy(aliases, kvm->arch.aliases, sizeof(struct kvm_mem_aliases));
-	aliases->aliases[alias->slot].flags |= KVM_ALIAS_INVALID;
-	old_aliases = kvm->arch.aliases;
-	rcu_assign_pointer(kvm->arch.aliases, aliases);
-	synchronize_srcu_expedited(&kvm->srcu);
-	kvm_mmu_zap_all(kvm);
-	kfree(old_aliases);
-
-	r = -ENOMEM;
-	aliases = kzalloc(sizeof(struct kvm_mem_aliases), GFP_KERNEL);
-	if (!aliases)
-		goto out_unlock;
-
-	memcpy(aliases, kvm->arch.aliases, sizeof(struct kvm_mem_aliases));
-
-	p = &aliases->aliases[alias->slot];
-	p->base_gfn = alias->guest_phys_addr >> PAGE_SHIFT;
-	p->npages = alias->memory_size >> PAGE_SHIFT;
-	p->target_gfn = alias->target_phys_addr >> PAGE_SHIFT;
-	p->flags &= ~(KVM_ALIAS_INVALID);
-
-	for (n = KVM_ALIAS_SLOTS; n > 0; --n)
-		if (aliases->aliases[n - 1].npages)
-			break;
-	aliases->naliases = n;
-
-	old_aliases = kvm->arch.aliases;
-	rcu_assign_pointer(kvm->arch.aliases, aliases);
-	synchronize_srcu_expedited(&kvm->srcu);
-	kfree(old_aliases);
-	r = 0;
-
-out_unlock:
-	mutex_unlock(&kvm->slots_lock);
-out:
-	return r;
-}
-
 static int kvm_vm_ioctl_get_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
 {
 	int r;
@@ -3056,7 +2947,6 @@ long kvm_arch_vm_ioctl(struct file *filp,
 	union {
 		struct kvm_pit_state ps;
 		struct kvm_pit_state2 ps2;
-		struct kvm_memory_alias alias;
 		struct kvm_pit_config pit_config;
 	} u;
 
@@ -3101,14 +2991,6 @@ long kvm_arch_vm_ioctl(struct file *filp,
 	case KVM_GET_NR_MMU_PAGES:
 		r = kvm_vm_ioctl_get_nr_mmu_pages(kvm);
 		break;
-	case KVM_SET_MEMORY_ALIAS:
-		r = -EFAULT;
-		if (copy_from_user(&u.alias, argp, sizeof(struct kvm_memory_alias)))
-			goto out;
-		r = kvm_vm_ioctl_set_memory_alias(kvm, &u.alias);
-		if (r)
-			goto out;
-		break;
 	case KVM_CREATE_IRQCHIP: {
 		struct kvm_pic *vpic;
 
@@ -5559,12 +5441,6 @@ struct  kvm *kvm_arch_create_vm(void)
 	if (!kvm)
 		return ERR_PTR(-ENOMEM);
 
-	kvm->arch.aliases = kzalloc(sizeof(struct kvm_mem_aliases), GFP_KERNEL);
-	if (!kvm->arch.aliases) {
-		kfree(kvm);
-		return ERR_PTR(-ENOMEM);
-	}
-
 	INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
 	INIT_LIST_HEAD(&kvm->arch.assigned_dev_head);
 
@@ -5622,7 +5498,6 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 	if (kvm->arch.ept_identity_pagetable)
 		put_page(kvm->arch.ept_identity_pagetable);
 	cleanup_srcu_struct(&kvm->srcu);
-	kfree(kvm->arch.aliases);
 	kfree(kvm);
 }
 

arch/x86/kvm/x86.h

@@ -65,13 +65,6 @@ static inline int is_paging(struct kvm_vcpu *vcpu)
 	return kvm_read_cr0_bits(vcpu, X86_CR0_PG);
 }
 
-static inline struct kvm_mem_aliases *kvm_aliases(struct kvm *kvm)
-{
-	return rcu_dereference_check(kvm->arch.aliases,
-			srcu_read_lock_held(&kvm->srcu)
-			|| lockdep_is_held(&kvm->slots_lock));
-}
-
 void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
 

include/linux/kvm.h

@@ -619,6 +619,7 @@ struct kvm_clock_data {
  */
 #define KVM_CREATE_VCPU           _IO(KVMIO,   0x41)
 #define KVM_GET_DIRTY_LOG         _IOW(KVMIO,  0x42, struct kvm_dirty_log)
+/* KVM_SET_MEMORY_ALIAS is obsolete: */
 #define KVM_SET_MEMORY_ALIAS      _IOW(KVMIO,  0x43, struct kvm_memory_alias)
 #define KVM_SET_NR_MMU_PAGES      _IO(KVMIO,   0x44)
 #define KVM_GET_NR_MMU_PAGES      _IO(KVMIO,   0x45)

include/linux/kvm_host.h

@@ -286,8 +286,6 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
 				int user_alloc);
 void kvm_disable_largepages(void);
 void kvm_arch_flush_shadow(struct kvm *kvm);
-gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn);
-gfn_t unalias_gfn_instantiation(struct kvm *kvm, gfn_t gfn);
 
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
 unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn);
@@ -564,10 +562,6 @@ static inline int mmu_notifier_retry(struct kvm_vcpu *vcpu, unsigned long mmu_se
 }
 #endif
 
-#ifndef KVM_ARCH_HAS_UNALIAS_INSTANTIATION
-#define unalias_gfn_instantiation unalias_gfn
-#endif
-
 #ifdef CONFIG_HAVE_KVM_IRQCHIP
 
 #define KVM_MAX_IRQ_ROUTES 1024

virt/kvm/kvm_main.c

@@ -841,7 +841,7 @@ int kvm_is_error_hva(unsigned long addr)
 }
 EXPORT_SYMBOL_GPL(kvm_is_error_hva);
 
-struct kvm_memory_slot *gfn_to_memslot_unaliased(struct kvm *kvm, gfn_t gfn)
+struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
 {
 	int i;
 	struct kvm_memslots *slots = kvm_memslots(kvm);
@@ -855,20 +855,13 @@ struct kvm_memory_slot *gfn_to_memslot_unaliased(struct kvm *kvm, gfn_t gfn)
 	}
 	return NULL;
 }
-EXPORT_SYMBOL_GPL(gfn_to_memslot_unaliased);
-
-struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
-{
-	gfn = unalias_gfn(kvm, gfn);
-	return gfn_to_memslot_unaliased(kvm, gfn);
-}
+EXPORT_SYMBOL_GPL(gfn_to_memslot);
 
 int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
 {
 	int i;
 	struct kvm_memslots *slots = kvm_memslots(kvm);
 
-	gfn = unalias_gfn_instantiation(kvm, gfn);
 	for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
 		struct kvm_memory_slot *memslot = &slots->memslots[i];
 
@@ -913,7 +906,6 @@ int memslot_id(struct kvm *kvm, gfn_t gfn)
 	struct kvm_memslots *slots = kvm_memslots(kvm);
 	struct kvm_memory_slot *memslot = NULL;
 
-	gfn = unalias_gfn(kvm, gfn);
 	for (i = 0; i < slots->nmemslots; ++i) {
 		memslot = &slots->memslots[i];
 
@@ -934,8 +926,7 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 {
 	struct kvm_memory_slot *slot;
 
-	gfn = unalias_gfn_instantiation(kvm, gfn);
-	slot = gfn_to_memslot_unaliased(kvm, gfn);
+	slot = gfn_to_memslot(kvm, gfn);
 	if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
 		return bad_hva();
 	return gfn_to_hva_memslot(slot, gfn);
@@ -1202,8 +1193,7 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
 {
 	struct kvm_memory_slot *memslot;
 
-	gfn = unalias_gfn(kvm, gfn);
-	memslot = gfn_to_memslot_unaliased(kvm, gfn);
+	memslot = gfn_to_memslot(kvm, gfn);
 	if (memslot && memslot->dirty_bitmap) {
 		unsigned long rel_gfn = gfn - memslot->base_gfn;