1 files changed, 257 insertions, 135 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a944be392d6..548f9253c19 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -44,6 +44,8 @@
 #include <linux/bitops.h>
 #include <linux/spinlock.h>
 #include <linux/compat.h>
+#include <linux/srcu.h>
+#include <linux/hugetlb.h>
 
 #include <asm/processor.h>
 #include <asm/io.h>
@@ -51,9 +53,7 @@
 #include <asm/pgtable.h>
 #include <asm-generic/bitops/le.h>
 
-#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 #include "coalesced_mmio.h"
-#endif
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/kvm.h>
@@ -86,6 +86,8 @@ static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
 static int hardware_enable_all(void);
 static void hardware_disable_all(void);
 
+static void kvm_io_bus_destroy(struct kvm_io_bus *bus);
+
 static bool kvm_rebooting;
 
 static bool largepages_enabled = true;
@@ -136,7 +138,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
 
         zalloc_cpumask_var(&cpus, GFP_ATOMIC);
 
-        spin_lock(&kvm->requests_lock);
+        raw_spin_lock(&kvm->requests_lock);
         me = smp_processor_id();
         kvm_for_each_vcpu(i, vcpu, kvm) {
                 if (test_and_set_bit(req, &vcpu->requests))
@@ -151,7 +153,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
                 smp_call_function_many(cpus, ack_flush, NULL, 1);
         else
                 called = false;
-        spin_unlock(&kvm->requests_lock);
+        raw_spin_unlock(&kvm->requests_lock);
         free_cpumask_var(cpus);
         return called;
 }
@@ -215,7 +217,7 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
                                              unsigned long address)
 {
         struct kvm *kvm = mmu_notifier_to_kvm(mn);
-        int need_tlb_flush;
+        int need_tlb_flush, idx;
 
         /*
          * When ->invalidate_page runs, the linux pte has been zapped
@@ -235,10 +237,12 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
          * pte after kvm_unmap_hva returned, without noticing the page
          * is going to be freed.
          */
+        idx = srcu_read_lock(&kvm->srcu);
         spin_lock(&kvm->mmu_lock);
         kvm->mmu_notifier_seq++;
         need_tlb_flush = kvm_unmap_hva(kvm, address);
         spin_unlock(&kvm->mmu_lock);
+        srcu_read_unlock(&kvm->srcu, idx);
 
         /* we've to flush the tlb before the pages can be freed */
         if (need_tlb_flush)
@@ -252,11 +256,14 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
                                         pte_t pte)
 {
         struct kvm *kvm = mmu_notifier_to_kvm(mn);
+        int idx;
 
+        idx = srcu_read_lock(&kvm->srcu);
         spin_lock(&kvm->mmu_lock);
         kvm->mmu_notifier_seq++;
         kvm_set_spte_hva(kvm, address, pte);
         spin_unlock(&kvm->mmu_lock);
+        srcu_read_unlock(&kvm->srcu, idx);
 }
 
 static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
@@ -265,8 +272,9 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
                                                     unsigned long end)
 {
         struct kvm *kvm = mmu_notifier_to_kvm(mn);
-        int need_tlb_flush = 0;
+        int need_tlb_flush = 0, idx;
 
+        idx = srcu_read_lock(&kvm->srcu);
         spin_lock(&kvm->mmu_lock);
         /*
          * The count increase must become visible at unlock time as no
@@ -277,6 +285,7 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
         for (; start < end; start += PAGE_SIZE)
                 need_tlb_flush |= kvm_unmap_hva(kvm, start);
         spin_unlock(&kvm->mmu_lock);
+        srcu_read_unlock(&kvm->srcu, idx);
 
         /* we've to flush the tlb before the pages can be freed */
         if (need_tlb_flush)
@@ -314,11 +323,13 @@ static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
                                               unsigned long address)
 {
         struct kvm *kvm = mmu_notifier_to_kvm(mn);
-        int young;
+        int young, idx;
 
+        idx = srcu_read_lock(&kvm->srcu);
         spin_lock(&kvm->mmu_lock);
         young = kvm_age_hva(kvm, address);
         spin_unlock(&kvm->mmu_lock);
+        srcu_read_unlock(&kvm->srcu, idx);
 
         if (young)
                 kvm_flush_remote_tlbs(kvm);
@@ -341,15 +352,26 @@ static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
         .change_pte             = kvm_mmu_notifier_change_pte,
         .release                = kvm_mmu_notifier_release,
 };
+
+static int kvm_init_mmu_notifier(struct kvm *kvm)
+{
+        kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
+        return mmu_notifier_register(&kvm->mmu_notifier, current->mm);
+}
+
+#else  /* !(CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER) */
+
+static int kvm_init_mmu_notifier(struct kvm *kvm)
+{
+        return 0;
+}
+
 #endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */
 
 static struct kvm *kvm_create_vm(void)
 {
-        int r = 0;
+        int r = 0, i;
         struct kvm *kvm = kvm_arch_create_vm();
-#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
-        struct page *page;
-#endif
 
         if (IS_ERR(kvm))
                 goto out;
@@ -363,39 +385,35 @@ static struct kvm *kvm_create_vm(void)
         INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list);
 #endif
 
-#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
-        page = alloc_page(GFP_KERNEL | __GFP_ZERO);
-        if (!page) {
-                r = -ENOMEM;
+        r = -ENOMEM;
+        kvm->memslots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
+        if (!kvm->memslots)
                 goto out_err;
-        }
-        kvm->coalesced_mmio_ring =
-                        (struct kvm_coalesced_mmio_ring *)page_address(page);
-#endif
-
-#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
-        {
-                kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
-                r = mmu_notifier_register(&kvm->mmu_notifier, current->mm);
-                if (r) {
-#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
-                        put_page(page);
-#endif
+        if (init_srcu_struct(&kvm->srcu))
+                goto out_err;
+        for (i = 0; i < KVM_NR_BUSES; i++) {
+                kvm->buses[i] = kzalloc(sizeof(struct kvm_io_bus),
+                                        GFP_KERNEL);
+                if (!kvm->buses[i]) {
+                        cleanup_srcu_struct(&kvm->srcu);
                         goto out_err;
                 }
         }
-#endif
+
+        r = kvm_init_mmu_notifier(kvm);
+        if (r) {
+                cleanup_srcu_struct(&kvm->srcu);
+                goto out_err;
+        }
 
         kvm->mm = current->mm;
         atomic_inc(&kvm->mm->mm_count);
         spin_lock_init(&kvm->mmu_lock);
-        spin_lock_init(&kvm->requests_lock);
-        kvm_io_bus_init(&kvm->pio_bus);
+        raw_spin_lock_init(&kvm->requests_lock);
         kvm_eventfd_init(kvm);
         mutex_init(&kvm->lock);
         mutex_init(&kvm->irq_lock);
-        kvm_io_bus_init(&kvm->mmio_bus);
-        init_rwsem(&kvm->slots_lock);
+        mutex_init(&kvm->slots_lock);
         atomic_set(&kvm->users_count, 1);
         spin_lock(&kvm_lock);
         list_add(&kvm->vm_list, &vm_list);
@@ -406,12 +424,12 @@ static struct kvm *kvm_create_vm(void)
 out:
         return kvm;
 
-#if defined(KVM_COALESCED_MMIO_PAGE_OFFSET) || \
-    (defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER))
 out_err:
         hardware_disable_all();
-#endif
 out_err_nodisable:
+        for (i = 0; i < KVM_NR_BUSES; i++)
+                kfree(kvm->buses[i]);
+        kfree(kvm->memslots);
         kfree(kvm);
         return ERR_PTR(r);
 }
@@ -446,13 +464,17 @@ static void kvm_free_physmem_slot(struct kvm_memory_slot *free,
 void kvm_free_physmem(struct kvm *kvm)
 {
         int i;
+        struct kvm_memslots *slots = kvm->memslots;
+
+        for (i = 0; i < slots->nmemslots; ++i)
+                kvm_free_physmem_slot(&slots->memslots[i], NULL);
 
-        for (i = 0; i < kvm->nmemslots; ++i)
-                kvm_free_physmem_slot(&kvm->memslots[i], NULL);
+        kfree(kvm->memslots);
 }
 
 static void kvm_destroy_vm(struct kvm *kvm)
 {
+        int i;
         struct mm_struct *mm = kvm->mm;
 
         kvm_arch_sync_events(kvm);
@@ -460,12 +482,9 @@ static void kvm_destroy_vm(struct kvm *kvm)
         list_del(&kvm->vm_list);
         spin_unlock(&kvm_lock);
         kvm_free_irq_routing(kvm);
-        kvm_io_bus_destroy(&kvm->pio_bus);
-        kvm_io_bus_destroy(&kvm->mmio_bus);
-#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
-        if (kvm->coalesced_mmio_ring != NULL)
-                free_page((unsigned long)kvm->coalesced_mmio_ring);
-#endif
+        for (i = 0; i < KVM_NR_BUSES; i++)
+                kvm_io_bus_destroy(kvm->buses[i]);
+        kvm_coalesced_mmio_free(kvm);
 #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
         mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
 #else
@@ -512,12 +531,13 @@ int __kvm_set_memory_region(struct kvm *kvm,
                             struct kvm_userspace_memory_region *mem,
                             int user_alloc)
 {
-        int r;
+        int r, flush_shadow = 0;
         gfn_t base_gfn;
         unsigned long npages;
         unsigned long i;
         struct kvm_memory_slot *memslot;
         struct kvm_memory_slot old, new;
+        struct kvm_memslots *slots, *old_memslots;
 
         r = -EINVAL;
         /* General sanity checks */
@@ -532,7 +552,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
         if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
                 goto out;
 
-        memslot = &kvm->memslots[mem->slot];
+        memslot = &kvm->memslots->memslots[mem->slot];
         base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
         npages = mem->memory_size >> PAGE_SHIFT;
 
@@ -553,7 +573,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
         /* Check for overlaps */
         r = -EEXIST;
         for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
-                struct kvm_memory_slot *s = &kvm->memslots[i];
+                struct kvm_memory_slot *s = &kvm->memslots->memslots[i];
 
                 if (s == memslot || !s->npages)
                         continue;
@@ -579,15 +599,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
                 memset(new.rmap, 0, npages * sizeof(*new.rmap));
 
                 new.user_alloc = user_alloc;
-                /*
-                 * hva_to_rmmap() serialzies with the mmu_lock and to be
-                 * safe it has to ignore memslots with !user_alloc &&
-                 * !userspace_addr.
-                 */
-                if (user_alloc)
-                        new.userspace_addr = mem->userspace_addr;
-                else
-                        new.userspace_addr = 0;
+                new.userspace_addr = mem->userspace_addr;
         }
         if (!npages)
                 goto skip_lpage;
@@ -642,8 +654,9 @@ skip_lpage:
                 if (!new.dirty_bitmap)
                         goto out_free;
                 memset(new.dirty_bitmap, 0, dirty_bytes);
+                /* destroy any largepage mappings for dirty tracking */
                 if (old.npages)
-                        kvm_arch_flush_shadow(kvm);
+                        flush_shadow = 1;
         }
 #else  /* not defined CONFIG_S390 */
         new.user_alloc = user_alloc;
@@ -651,36 +664,72 @@ skip_lpage:
                 new.userspace_addr = mem->userspace_addr;
 #endif /* not defined CONFIG_S390 */
 
-        if (!npages)
+        if (!npages) {
+                r = -ENOMEM;
+                slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
+                if (!slots)
+                        goto out_free;
+                memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
+                if (mem->slot >= slots->nmemslots)
+                        slots->nmemslots = mem->slot + 1;
+                slots->memslots[mem->slot].flags |= KVM_MEMSLOT_INVALID;
+
+                old_memslots = kvm->memslots;
+                rcu_assign_pointer(kvm->memslots, slots);
+                synchronize_srcu_expedited(&kvm->srcu);
+                /* From this point no new shadow pages pointing to a deleted
+                 * memslot will be created.
+                 *
+                 * validation of sp->gfn happens in:
+                 *      - gfn_to_hva (kvm_read_guest, gfn_to_pfn)
+                 *      - kvm_is_visible_gfn (mmu_check_roots)
+                 */
                 kvm_arch_flush_shadow(kvm);
+                kfree(old_memslots);
+        }
 
-        spin_lock(&kvm->mmu_lock);
-        if (mem->slot >= kvm->nmemslots)
-                kvm->nmemslots = mem->slot + 1;
-
-        *memslot = new;
-        spin_unlock(&kvm->mmu_lock);
-
-        r = kvm_arch_set_memory_region(kvm, mem, old, user_alloc);
-        if (r) {
-                spin_lock(&kvm->mmu_lock);
-                *memslot = old;
-                spin_unlock(&kvm->mmu_lock);
+        r = kvm_arch_prepare_memory_region(kvm, &new, old, mem, user_alloc);
+        if (r)
                 goto out_free;
-        }
 
-        kvm_free_physmem_slot(&old, npages ? &new : NULL);
-        /* Slot deletion case: we have to update the current slot */
-        spin_lock(&kvm->mmu_lock);
-        if (!npages)
-                *memslot = old;
-        spin_unlock(&kvm->mmu_lock);
 #ifdef CONFIG_DMAR
         /* map the pages in iommu page table */
-        r = kvm_iommu_map_pages(kvm, base_gfn, npages);
-        if (r)
-                goto out;
+        if (npages) {
+                r = kvm_iommu_map_pages(kvm, &new);
+                if (r)
+                        goto out_free;
+        }
 #endif
+
+        r = -ENOMEM;
+        slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
+        if (!slots)
+                goto out_free;
+        memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
+        if (mem->slot >= slots->nmemslots)
+                slots->nmemslots = mem->slot + 1;
+
+        /* actual memory is freed via old in kvm_free_physmem_slot below */
+        if (!npages) {
+                new.rmap = NULL;
+                new.dirty_bitmap = NULL;
+                for (i = 0; i < KVM_NR_PAGE_SIZES - 1; ++i)
+                        new.lpage_info[i] = NULL;
+        }
+
+        slots->memslots[mem->slot] = new;
+        old_memslots = kvm->memslots;
+        rcu_assign_pointer(kvm->memslots, slots);
+        synchronize_srcu_expedited(&kvm->srcu);
+
+        kvm_arch_commit_memory_region(kvm, mem, old, user_alloc);
+
+        kvm_free_physmem_slot(&old, &new);
+        kfree(old_memslots);
+
+        if (flush_shadow)
+                kvm_arch_flush_shadow(kvm);
+
         return 0;
 
 out_free:
@@ -697,9 +746,9 @@ int kvm_set_memory_region(struct kvm *kvm,
 {
         int r;
 
-        down_write(&kvm->slots_lock);
+        mutex_lock(&kvm->slots_lock);
         r = __kvm_set_memory_region(kvm, mem, user_alloc);
-        up_write(&kvm->slots_lock);
+        mutex_unlock(&kvm->slots_lock);
         return r;
 }
 EXPORT_SYMBOL_GPL(kvm_set_memory_region);
@@ -726,7 +775,7 @@ int kvm_get_dirty_log(struct kvm *kvm,
         if (log->slot >= KVM_MEMORY_SLOTS)
                 goto out;
 
-        memslot = &kvm->memslots[log->slot];
+        memslot = &kvm->memslots->memslots[log->slot];
         r = -ENOENT;
         if (!memslot->dirty_bitmap)
                 goto out;
@@ -780,9 +829,10 @@ EXPORT_SYMBOL_GPL(kvm_is_error_hva);
 struct kvm_memory_slot *gfn_to_memslot_unaliased(struct kvm *kvm, gfn_t gfn)
 {
         int i;
+        struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
 
-        for (i = 0; i < kvm->nmemslots; ++i) {
-                struct kvm_memory_slot *memslot = &kvm->memslots[i];
+        for (i = 0; i < slots->nmemslots; ++i) {
+                struct kvm_memory_slot *memslot = &slots->memslots[i];
 
                 if (gfn >= memslot->base_gfn
                     && gfn < memslot->base_gfn + memslot->npages)
@@ -801,10 +851,14 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
 int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
 {
         int i;
+        struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
 
-        gfn = unalias_gfn(kvm, gfn);
+        gfn = unalias_gfn_instantiation(kvm, gfn);
         for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
-                struct kvm_memory_slot *memslot = &kvm->memslots[i];
+                struct kvm_memory_slot *memslot = &slots->memslots[i];
+
+                if (memslot->flags & KVM_MEMSLOT_INVALID)
+                        continue;
 
                 if (gfn >= memslot->base_gfn
                     && gfn < memslot->base_gfn + memslot->npages)
@@ -814,33 +868,68 @@ int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);
 
+unsigned long kvm_host_page_size(struct kvm *kvm, gfn_t gfn)
+{
+        struct vm_area_struct *vma;
+        unsigned long addr, size;
+
+        size = PAGE_SIZE;
+
+        addr = gfn_to_hva(kvm, gfn);
+        if (kvm_is_error_hva(addr))
+                return PAGE_SIZE;
+
+        down_read(&current->mm->mmap_sem);
+        vma = find_vma(current->mm, addr);
+        if (!vma)
+                goto out;
+
+        size = vma_kernel_pagesize(vma);
+
+out:
+        up_read(&current->mm->mmap_sem);
+
+        return size;
+}
+
+int memslot_id(struct kvm *kvm, gfn_t gfn)
+{
+        int i;
+        struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
+        struct kvm_memory_slot *memslot = NULL;
+
+        gfn = unalias_gfn(kvm, gfn);
+        for (i = 0; i < slots->nmemslots; ++i) {
+                memslot = &slots->memslots[i];
+
+                if (gfn >= memslot->base_gfn
+                    && gfn < memslot->base_gfn + memslot->npages)
+                        break;
+        }
+
+        return memslot - slots->memslots;
+}
+
 unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 {
         struct kvm_memory_slot *slot;
 
-        gfn = unalias_gfn(kvm, gfn);
+        gfn = unalias_gfn_instantiation(kvm, gfn);
         slot = gfn_to_memslot_unaliased(kvm, gfn);
-        if (!slot)
+        if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
                 return bad_hva();
         return (slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE);
 }
 EXPORT_SYMBOL_GPL(gfn_to_hva);
 
-pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
+static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr)
 {
         struct page *page[1];
-        unsigned long addr;
         int npages;
         pfn_t pfn;
 
         might_sleep();
 
-        addr = gfn_to_hva(kvm, gfn);
-        if (kvm_is_error_hva(addr)) {
-                get_page(bad_page);
-                return page_to_pfn(bad_page);
-        }
-
         npages = get_user_pages_fast(addr, 1, 1, page);
 
         if (unlikely(npages != 1)) {
@@ -865,8 +954,32 @@ pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
         return pfn;
 }
 
+pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
+{
+        unsigned long addr;
+
+        addr = gfn_to_hva(kvm, gfn);
+        if (kvm_is_error_hva(addr)) {
+                get_page(bad_page);
+                return page_to_pfn(bad_page);
+        }
+
+        return hva_to_pfn(kvm, addr);
+}
 EXPORT_SYMBOL_GPL(gfn_to_pfn);
 
+static unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
+{
+        return (slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE);
+}
+
+pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
+                         struct kvm_memory_slot *slot, gfn_t gfn)
+{
+        unsigned long addr = gfn_to_hva_memslot(slot, gfn);
+        return hva_to_pfn(kvm, addr);
+}
+
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 {
         pfn_t pfn;
@@ -1854,12 +1967,7 @@ static struct notifier_block kvm_reboot_notifier = {
         .priority = 0,
 };
 
-void kvm_io_bus_init(struct kvm_io_bus *bus)
-{
-        memset(bus, 0, sizeof(*bus));
-}
-
-void kvm_io_bus_destroy(struct kvm_io_bus *bus)
+static void kvm_io_bus_destroy(struct kvm_io_bus *bus)
 {
         int i;
 
@@ -1868,13 +1976,15 @@ void kvm_io_bus_destroy(struct kvm_io_bus *bus)
 
                 kvm_iodevice_destructor(pos);
         }
+        kfree(bus);
 }
 
 /* kvm_io_bus_write - called under kvm->slots_lock */
-int kvm_io_bus_write(struct kvm_io_bus *bus, gpa_t addr,
+int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
                      int len, const void *val)
 {
         int i;
+        struct kvm_io_bus *bus = rcu_dereference(kvm->buses[bus_idx]);
         for (i = 0; i < bus->dev_count; i++)
                 if (!kvm_iodevice_write(bus->devs[i], addr, len, val))
                         return 0;
@@ -1882,59 +1992,71 @@ int kvm_io_bus_write(struct kvm_io_bus *bus, gpa_t addr,
 }
 
 /* kvm_io_bus_read - called under kvm->slots_lock */
-int kvm_io_bus_read(struct kvm_io_bus *bus, gpa_t addr, int len, void *val)
+int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
+                    int len, void *val)
 {
         int i;
+        struct kvm_io_bus *bus = rcu_dereference(kvm->buses[bus_idx]);
+
         for (i = 0; i < bus->dev_count; i++)
                 if (!kvm_iodevice_read(bus->devs[i], addr, len, val))
                         return 0;
         return -EOPNOTSUPP;
 }
 
-int kvm_io_bus_register_dev(struct kvm *kvm, struct kvm_io_bus *bus,
-                             struct kvm_io_device *dev)
+/* Caller must hold slots_lock. */
+int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx,
+                            struct kvm_io_device *dev)
 {
-        int ret;
-
-        down_write(&kvm->slots_lock);
-        ret = __kvm_io_bus_register_dev(bus, dev);
-        up_write(&kvm->slots_lock);
+        struct kvm_io_bus *new_bus, *bus;
 
-        return ret;
-}
-
-/* An unlocked version. Caller must have write lock on slots_lock. */
-int __kvm_io_bus_register_dev(struct kvm_io_bus *bus,
-                              struct kvm_io_device *dev)
-{
+        bus = kvm->buses[bus_idx];
         if (bus->dev_count > NR_IOBUS_DEVS-1)
                 return -ENOSPC;
 
-        bus->devs[bus->dev_count++] = dev;
+        new_bus = kzalloc(sizeof(struct kvm_io_bus), GFP_KERNEL);
+        if (!new_bus)
+                return -ENOMEM;
+        memcpy(new_bus, bus, sizeof(struct kvm_io_bus));
+        new_bus->devs[new_bus->dev_count++] = dev;
+        rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
+        synchronize_srcu_expedited(&kvm->srcu);
+        kfree(bus);
 
         return 0;
 }
 
-void kvm_io_bus_unregister_dev(struct kvm *kvm,
-                               struct kvm_io_bus *bus,
-                               struct kvm_io_device *dev)
+/* Caller must hold slots_lock. */
+int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
+                              struct kvm_io_device *dev)
 {
-        down_write(&kvm->slots_lock);
-        __kvm_io_bus_unregister_dev(bus, dev);
-        up_write(&kvm->slots_lock);
-}
+        int i, r;
+        struct kvm_io_bus *new_bus, *bus;
 
-/* An unlocked version. Caller must have write lock on slots_lock. */
-void __kvm_io_bus_unregister_dev(struct kvm_io_bus *bus,
-                                 struct kvm_io_device *dev)
-{
-        int i;
+        new_bus = kzalloc(sizeof(struct kvm_io_bus), GFP_KERNEL);
+        if (!new_bus)
+                return -ENOMEM;
 
-        for (i = 0; i < bus->dev_count; i++)
-                if (bus->devs[i] == dev) {
-                        bus->devs[i] = bus->devs[--bus->dev_count];
+        bus = kvm->buses[bus_idx];
+        memcpy(new_bus, bus, sizeof(struct kvm_io_bus));
+
+        r = -ENOENT;
+        for (i = 0; i < new_bus->dev_count; i++)
+                if (new_bus->devs[i] == dev) {
+                        r = 0;
+                        new_bus->devs[i] = new_bus->devs[--new_bus->dev_count];
                         break;
                 }
+
+        if (r) {
+                kfree(new_bus);
+                return r;
+        }
+
+        rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
+        synchronize_srcu_expedited(&kvm->srcu);
+        kfree(bus);
+        return r;
 }
 
 static struct notifier_block kvm_cpu_notifier = {