[PATCH v10 9/9] KVM: Enable and expose KVM_MEM_PRIVATE

[Chao Peng]

Register/unregister private memslot to fd-based memory backing store
restrictedmem and implement the callbacks for restrictedmem_notifier:
  - invalidate_start()/invalidate_end() to zap the existing memory
    mappings in the KVM page table.
  - error() to request KVM_REQ_MEMORY_MCE and later exit to userspace
    with KVM_EXIT_SHUTDOWN.

Expose KVM_MEM_PRIVATE for memslot and KVM_MEMORY_ATTRIBUTE_PRIVATE for
KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES to userspace but either are
controlled by kvm_arch_has_private_mem() which should be rewritten by
architecture code.

Co-developed-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
---
 arch/x86/include/asm/kvm_host.h |   1 +
 arch/x86/kvm/x86.c              |  13 +++
 include/linux/kvm_host.h        |   3 +
 virt/kvm/kvm_main.c             | 179 +++++++++++++++++++++++++++++++-
 4 files changed, 191 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7772ab37ac89..27ef31133352 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -114,6 +114,7 @@
        KVM_ARCH_REQ_FLAGS(31, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_HV_TLB_FLUSH \
        KVM_ARCH_REQ_FLAGS(32, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_MEMORY_MCE             KVM_ARCH_REQ(33)
 
 #define CR0_RESERVED_BITS                                               \
        (~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5aefcff614d2..c67e22f3e2ee 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6587,6 +6587,13 @@ int kvm_arch_pm_notifier(struct kvm *kvm, unsigned long 
state)
 }
 #endif /* CONFIG_HAVE_KVM_PM_NOTIFIER */
 
+#ifdef CONFIG_HAVE_KVM_RESTRICTED_MEM
+void kvm_arch_memory_mce(struct kvm *kvm)
+{
+       kvm_make_all_cpus_request(kvm, KVM_REQ_MEMORY_MCE);
+}
+#endif
+
 static int kvm_vm_ioctl_get_clock(struct kvm *kvm, void __user *argp)
 {
        struct kvm_clock_data data = { 0 };
@@ -10357,6 +10364,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
                if (kvm_check_request(KVM_REQ_UPDATE_CPU_DIRTY_LOGGING, vcpu))
                        static_call(kvm_x86_update_cpu_dirty_logging)(vcpu);
+
+               if (kvm_check_request(KVM_REQ_MEMORY_MCE, vcpu)) {
+                       vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
+                       r = 0;
+                       goto out;
+               }
        }
 
        if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win ||
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 153842bb33df..f032d878e034 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -590,6 +590,7 @@ struct kvm_memory_slot {
        struct file *restricted_file;
        loff_t restricted_offset;
        struct restrictedmem_notifier notifier;
+       struct kvm *kvm;
 };
 
 static inline bool kvm_slot_can_be_private(const struct kvm_memory_slot *slot)
@@ -2363,6 +2364,8 @@ static inline int kvm_restricted_mem_get_pfn(struct 
kvm_memory_slot *slot,
        *pfn = page_to_pfn(page);
        return ret;
 }
+
+void kvm_arch_memory_mce(struct kvm *kvm);
 #endif /* CONFIG_HAVE_KVM_RESTRICTED_MEM */
 
 #endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e107afea32f0..ac835fc77273 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -936,6 +936,121 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)
 
 #endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */
 
+#ifdef CONFIG_HAVE_KVM_RESTRICTED_MEM
+static bool restrictedmem_range_is_valid(struct kvm_memory_slot *slot,
+                                        pgoff_t start, pgoff_t end,
+                                        gfn_t *gfn_start, gfn_t *gfn_end)
+{
+       unsigned long base_pgoff = slot->restricted_offset >> PAGE_SHIFT;
+
+       if (start > base_pgoff)
+               *gfn_start = slot->base_gfn + start - base_pgoff;
+       else
+               *gfn_start = slot->base_gfn;
+
+       if (end < base_pgoff + slot->npages)
+               *gfn_end = slot->base_gfn + end - base_pgoff;
+       else
+               *gfn_end = slot->base_gfn + slot->npages;
+
+       if (*gfn_start >= *gfn_end)
+               return false;
+
+       return true;
+}
+
+static void kvm_restrictedmem_invalidate_begin(struct restrictedmem_notifier 
*notifier,
+                                              pgoff_t start, pgoff_t end)
+{
+       struct kvm_memory_slot *slot = container_of(notifier,
+                                                   struct kvm_memory_slot,
+                                                   notifier);
+       struct kvm *kvm = slot->kvm;
+       gfn_t gfn_start, gfn_end;
+       struct kvm_gfn_range gfn_range;
+       int idx;
+
+       if (!restrictedmem_range_is_valid(slot, start, end,
+                                         &gfn_start, &gfn_end))
+               return;
+
+       gfn_range.start = gfn_start;
+       gfn_range.end = gfn_end;
+       gfn_range.slot = slot;
+       gfn_range.pte = __pte(0);
+       gfn_range.may_block = true;
+
+       idx = srcu_read_lock(&kvm->srcu);
+       KVM_MMU_LOCK(kvm);
+
+       kvm_mmu_invalidate_begin(kvm);
+       kvm_mmu_invalidate_range_add(kvm, gfn_start, gfn_end);
+       if (kvm_unmap_gfn_range(kvm, &gfn_range))
+               kvm_flush_remote_tlbs(kvm);
+
+       KVM_MMU_UNLOCK(kvm);
+       srcu_read_unlock(&kvm->srcu, idx);
+}
+
+static void kvm_restrictedmem_invalidate_end(struct restrictedmem_notifier 
*notifier,
+                                            pgoff_t start, pgoff_t end)
+{
+       struct kvm_memory_slot *slot = container_of(notifier,
+                                                   struct kvm_memory_slot,
+                                                   notifier);
+       struct kvm *kvm = slot->kvm;
+       gfn_t gfn_start, gfn_end;
+
+       if (!restrictedmem_range_is_valid(slot, start, end,
+                                         &gfn_start, &gfn_end))
+               return;
+
+       KVM_MMU_LOCK(kvm);
+       kvm_mmu_invalidate_end(kvm);
+       KVM_MMU_UNLOCK(kvm);
+}
+
+static void kvm_restrictedmem_error(struct restrictedmem_notifier *notifier,
+                                   pgoff_t start, pgoff_t end)
+{
+       struct kvm_memory_slot *slot = container_of(notifier,
+                                                   struct kvm_memory_slot,
+                                                   notifier);
+       kvm_arch_memory_mce(slot->kvm);
+}
+
+static struct restrictedmem_notifier_ops kvm_restrictedmem_notifier_ops = {
+       .invalidate_start = kvm_restrictedmem_invalidate_begin,
+       .invalidate_end = kvm_restrictedmem_invalidate_end,
+       .error = kvm_restrictedmem_error,
+};
+
+static inline void kvm_restrictedmem_register(struct kvm_memory_slot *slot)
+{
+       slot->notifier.ops = &kvm_restrictedmem_notifier_ops;
+       restrictedmem_register_notifier(slot->restricted_file, &slot->notifier);
+}
+
+static inline void kvm_restrictedmem_unregister(struct kvm_memory_slot *slot)
+{
+       restrictedmem_unregister_notifier(slot->restricted_file,
+                                         &slot->notifier);
+}
+
+#else /* !CONFIG_HAVE_KVM_RESTRICTED_MEM */
+
+static inline void kvm_restrictedmem_register(struct kvm_memory_slot *slot)
+{
+       WARN_ON_ONCE(1);
+}
+
+static inline void kvm_restrictedmem_unregister(struct kvm_memory_slot *slot)
+{
+       WARN_ON_ONCE(1);
+}
+
+#endif /* CONFIG_HAVE_KVM_RESTRICTED_MEM */
+
 #ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
 static int kvm_pm_notifier_call(struct notifier_block *bl,
                                unsigned long state,
@@ -980,6 +1095,11 @@ static void kvm_destroy_dirty_bitmap(struct 
kvm_memory_slot *memslot)
 /* This does not remove the slot from struct kvm_memslots data structures */
 static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
 {
+       if (slot->flags & KVM_MEM_PRIVATE) {
+               kvm_restrictedmem_unregister(slot);
+               fput(slot->restricted_file);
+       }
+
        kvm_destroy_dirty_bitmap(slot);
 
        kvm_arch_free_memslot(kvm, slot);
@@ -1551,10 +1671,14 @@ static void kvm_replace_memslot(struct kvm *kvm,
        }
 }
 
-static int check_memory_region_flags(const struct kvm_user_mem_region *mem)
+static int check_memory_region_flags(struct kvm *kvm,
+                                    const struct kvm_user_mem_region *mem)
 {
        u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
 
+       if (kvm_arch_has_private_mem(kvm))
+               valid_flags |= KVM_MEM_PRIVATE;
+
 #ifdef __KVM_HAVE_READONLY_MEM
        valid_flags |= KVM_MEM_READONLY;
 #endif
@@ -1630,6 +1754,9 @@ static int kvm_prepare_memory_region(struct kvm *kvm,
 {
        int r;
 
+       if (change == KVM_MR_CREATE && new->flags & KVM_MEM_PRIVATE)
+               kvm_restrictedmem_register(new);
+
        /*
         * If dirty logging is disabled, nullify the bitmap; the old bitmap
         * will be freed on "commit".  If logging is enabled in both old and
@@ -1658,6 +1785,9 @@ static int kvm_prepare_memory_region(struct kvm *kvm,
        if (r && new && new->dirty_bitmap && (!old || !old->dirty_bitmap))
                kvm_destroy_dirty_bitmap(new);
 
+       if (r && change == KVM_MR_CREATE && new->flags & KVM_MEM_PRIVATE)
+               kvm_restrictedmem_unregister(new);
+
        return r;
 }
 
@@ -1963,7 +2093,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
        int as_id, id;
        int r;
 
-       r = check_memory_region_flags(mem);
+       r = check_memory_region_flags(kvm, mem);
        if (r)
                return r;
 
@@ -1982,6 +2112,10 @@ int __kvm_set_memory_region(struct kvm *kvm,
             !access_ok((void __user *)(unsigned long)mem->userspace_addr,
                        mem->memory_size))
                return -EINVAL;
+       if (mem->flags & KVM_MEM_PRIVATE &&
+               (mem->restricted_offset & (PAGE_SIZE - 1) ||
+                mem->restricted_offset > U64_MAX - mem->memory_size))
+               return -EINVAL;
        if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
                return -EINVAL;
        if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
@@ -2020,6 +2154,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
                if ((kvm->nr_memslot_pages + npages) < kvm->nr_memslot_pages)
                        return -EINVAL;
        } else { /* Modify an existing slot. */
+               /* Private memslots are immutable, they can only be deleted. */
+               if (mem->flags & KVM_MEM_PRIVATE)
+                       return -EINVAL;
                if ((mem->userspace_addr != old->userspace_addr) ||
                    (npages != old->npages) ||
                    ((mem->flags ^ old->flags) & KVM_MEM_READONLY))
@@ -2048,10 +2185,28 @@ int __kvm_set_memory_region(struct kvm *kvm,
        new->npages = npages;
        new->flags = mem->flags;
        new->userspace_addr = mem->userspace_addr;
+       if (mem->flags & KVM_MEM_PRIVATE) {
+               new->restricted_file = fget(mem->restricted_fd);
+               if (!new->restricted_file ||
+                   !file_is_restrictedmem(new->restricted_file)) {
+                       r = -EINVAL;
+                       goto out;
+               }
+               new->restricted_offset = mem->restricted_offset;
+       }
+
+       new->kvm = kvm;
 
        r = kvm_set_memslot(kvm, old, new, change);
        if (r)
-               kfree(new);
+               goto out;
+
+       return 0;
+
+out:
+       if (new->restricted_file)
+               fput(new->restricted_file);
+       kfree(new);
        return r;
 }
 EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
@@ -2351,6 +2506,8 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 #ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES
 static u64 kvm_supported_mem_attributes(struct kvm *kvm)
 {
+       if (kvm_arch_has_private_mem(kvm))
+               return KVM_MEMORY_ATTRIBUTE_PRIVATE;
        return 0;
 }
 
@@ -4822,16 +4979,28 @@ static long kvm_vm_ioctl(struct file *filp,
        }
        case KVM_SET_USER_MEMORY_REGION: {
                struct kvm_user_mem_region mem;
-               unsigned long size = sizeof(struct kvm_userspace_memory_region);
+               unsigned int flags_offset = offsetof(typeof(mem), flags);
+               unsigned long size;
+               u32 flags;
 
                kvm_sanity_check_user_mem_region_alias();
 
+               memset(&mem, 0, sizeof(mem));
+
                r = -EFAULT;
+               if (get_user(flags, (u32 __user *)(argp + flags_offset)))
+                       goto out;
+
+               if (flags & KVM_MEM_PRIVATE)
+                       size = sizeof(struct kvm_userspace_memory_region_ext);
+               else
+                       size = sizeof(struct kvm_userspace_memory_region);
+
                if (copy_from_user(&mem, argp, size))
                        goto out;
 
                r = -EINVAL;
-               if (mem.flags & KVM_MEM_PRIVATE)
+               if ((flags ^ mem.flags) & KVM_MEM_PRIVATE)
                        goto out;
 
                r = kvm_vm_ioctl_set_memory_region(kvm, &mem);
-- 
2.25.1