KVM: Support assigning userspace memory to the guest

Instead of having the kernel allocate memory to the guest, let userspace
allocate it and pass the address to the kernel.

This is required for s390 support, but also enables features like memory
sharing and using hugetlbfs backed memory.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 70 insertions, 11 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index a1983d2d5b8f..22b143feb66d 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -40,6 +40,7 @@
 #include <linux/anon_inodes.h>
 #include <linux/profile.h>
 #include <linux/kvm_para.h>
+#include <linux/pagemap.h>
 
 #include <asm/processor.h>
 #include <asm/msr.h>
@@ -300,19 +301,40 @@ static struct kvm *kvm_create_vm(void)
         return kvm;
 }
 
+static void kvm_free_userspace_physmem(struct kvm_memory_slot *free)
+{
+        int i;
+
+        for (i = 0; i < free->npages; ++i) {
+                if (free->phys_mem[i]) {
+                        if (!PageReserved(free->phys_mem[i]))
+                                SetPageDirty(free->phys_mem[i]);
+                        page_cache_release(free->phys_mem[i]);
+                }
+        }
+}
+
+static void kvm_free_kernel_physmem(struct kvm_memory_slot *free)
+{
+        int i;
+
+        for (i = 0; i < free->npages; ++i)
+                if (free->phys_mem[i])
+                        __free_page(free->phys_mem[i]);
+}
+
 /*
  * Free any memory in @free but not in @dont.
  */
 static void kvm_free_physmem_slot(struct kvm_memory_slot *free,
                                   struct kvm_memory_slot *dont)
 {
-        int i;
-
         if (!dont || free->phys_mem != dont->phys_mem)
                 if (free->phys_mem) {
-                        for (i = 0; i < free->npages; ++i)
-                                if (free->phys_mem[i])
-                                        __free_page(free->phys_mem[i]);
+                        if (free->user_alloc)
+                                kvm_free_userspace_physmem(free);
+                        else
+                                kvm_free_kernel_physmem(free);
                         vfree(free->phys_mem);
                 }
         if (!dont || free->rmap != dont->rmap)
@@ -652,7 +674,9 @@ EXPORT_SYMBOL_GPL(fx_init);
  * Discontiguous memory is allowed, mostly for framebuffers.
  */
 static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
-                                          struct kvm_memory_region *mem)
+                                          struct
+                                          kvm_userspace_memory_region *mem,
+                                          int user_alloc)
 {
         int r;
         gfn_t base_gfn;
@@ -728,11 +752,27 @@ static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
 
                 memset(new.phys_mem, 0, npages * sizeof(struct page *));
                 memset(new.rmap, 0, npages * sizeof(*new.rmap));
-                for (i = 0; i < npages; ++i) {
-                        new.phys_mem[i] = alloc_page(GFP_HIGHUSER
-                                                     | __GFP_ZERO);
-                        if (!new.phys_mem[i])
+                if (user_alloc) {
+                        unsigned long pages_num;
+
+                        new.user_alloc = 1;
+                        down_read(&current->mm->mmap_sem);
+
+                        pages_num = get_user_pages(current, current->mm,
+                                                   mem->userspace_addr,
+                                                   npages, 1, 1, new.phys_mem,
+                                                   NULL);
+
+                        up_read(&current->mm->mmap_sem);
+                        if (pages_num != npages)
                                 goto out_unlock;
+                } else {
+                        for (i = 0; i < npages; ++i) {
+                                new.phys_mem[i] = alloc_page(GFP_HIGHUSER
+                                                             | __GFP_ZERO);
+                                if (!new.phys_mem[i])
+                                        goto out_unlock;
+                        }
                 }
         }
 
@@ -3108,11 +3148,29 @@ static long kvm_vm_ioctl(struct file *filp,
                 break;
         case KVM_SET_MEMORY_REGION: {
                 struct kvm_memory_region kvm_mem;
+                struct kvm_userspace_memory_region kvm_userspace_mem;
 
                 r = -EFAULT;
                 if (copy_from_user(&kvm_mem, argp, sizeof kvm_mem))
                         goto out;
-                r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_mem);
+                kvm_userspace_mem.slot = kvm_mem.slot;
+                kvm_userspace_mem.flags = kvm_mem.flags;
+                kvm_userspace_mem.guest_phys_addr = kvm_mem.guest_phys_addr;
+                kvm_userspace_mem.memory_size = kvm_mem.memory_size;
+                r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem, 0);
+                if (r)
+                        goto out;
+                break;
+        }
+        case KVM_SET_USER_MEMORY_REGION: {
+                struct kvm_userspace_memory_region kvm_userspace_mem;
+
+                r = -EFAULT;
+                if (copy_from_user(&kvm_userspace_mem, argp,
+                                                sizeof kvm_userspace_mem))
+                        goto out;
+
+                r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem, 1);
                 if (r)
                         goto out;
                 break;
@@ -3332,6 +3390,7 @@ static long kvm_dev_ioctl(struct file *filp,
                 case KVM_CAP_IRQCHIP:
                 case KVM_CAP_HLT:
                 case KVM_CAP_MMU_SHADOW_CACHE_CONTROL:
+                case KVM_CAP_USER_MEMORY:
                         r = 1;
                         break;
                 default: