[RFC][PATCH v2 14/21] kvm: register in mm_struct

[Fengguang Wu]

VM is associated with an address space and not a specific thread.

>From Documentation/virtual/kvm/api.txt:
   Only run VM ioctls from the same process (address space) that was used
   to create the VM.

CC: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
CC: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
---
 include/linux/mm_types.h |   11 +++++++++++
 virt/kvm/kvm_main.c      |    3 +++
 2 files changed, 14 insertions(+)

--- linux.orig/include/linux/mm_types.h	2018-12-23 19:58:06.993417137 +0800
+++ linux/include/linux/mm_types.h	2018-12-23 19:58:06.993417137 +0800
@@ -27,6 +27,7 @@ typedef int vm_fault_t;
 struct address_space;
 struct mem_cgroup;
 struct hmm;
+struct kvm;
 
 /*
  * Each physical page in the system has a struct page associated with
@@ -496,6 +497,10 @@ struct mm_struct {
 		/* HMM needs to track a few things per mm */
 		struct hmm *hmm;
 #endif
+
+#if IS_ENABLED(CONFIG_KVM)
+		struct kvm *kvm;
+#endif
 	} __randomize_layout;
 
 	/*
@@ -507,6 +512,12 @@ struct mm_struct {
 
 extern struct mm_struct init_mm;
 
+#if IS_ENABLED(CONFIG_KVM)
+static inline struct kvm *mm_kvm(struct mm_struct *mm) { return mm->kvm; }
+#else
+static inline struct kvm *mm_kvm(struct mm_struct *mm) { return NULL; }
+#endif
+
 /* Pointer magic because the dynamic array size confuses some compilers. */
 static inline void mm_init_cpumask(struct mm_struct *mm)
 {
--- linux.orig/virt/kvm/kvm_main.c	2018-12-23 19:58:06.993417137 +0800
+++ linux/virt/kvm/kvm_main.c	2018-12-23 19:58:06.993417137 +0800
@@ -727,6 +727,7 @@ static void kvm_destroy_vm(struct kvm *k
 	struct mm_struct *mm = kvm->mm;
 
 	kvm_uevent_notify_change(KVM_EVENT_DESTROY_VM, kvm);
+	mm->kvm = NULL;
 	kvm_destroy_vm_debugfs(kvm);
 	kvm_arch_sync_events(kvm);
 	spin_lock(&kvm_lock);
@@ -3224,6 +3225,8 @@ static int kvm_dev_ioctl_create_vm(unsig
 		fput(file);
 		return -ENOMEM;
 	}
+
+	kvm->mm->kvm = kvm;
 	kvm_uevent_notify_change(KVM_EVENT_CREATE_VM, kvm);
 
 	fd_install(r, file);