KVM: use SRCU for dirty log

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 41 insertions, 8 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 43da65feed49..e7488350ca16 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2415,27 +2415,60 @@ static int kvm_vm_ioctl_reinject(struct kvm *kvm,
 int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
                                       struct kvm_dirty_log *log)
 {
-        int r;
-        int n;
+        int r, n, i;
         struct kvm_memory_slot *memslot;
-        int is_dirty = 0;
+        unsigned long is_dirty = 0;
+        unsigned long *dirty_bitmap = NULL;
 
         down_write(&kvm->slots_lock);
 
-        r = kvm_get_dirty_log(kvm, log, &is_dirty);
-        if (r)
+        r = -EINVAL;
+        if (log->slot >= KVM_MEMORY_SLOTS)
+                goto out;
+
+        memslot = &kvm->memslots->memslots[log->slot];
+        r = -ENOENT;
+        if (!memslot->dirty_bitmap)
+                goto out;
+
+        n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+
+        r = -ENOMEM;
+        dirty_bitmap = vmalloc(n);
+        if (!dirty_bitmap)
                 goto out;
+        memset(dirty_bitmap, 0, n);
+
+        for (i = 0; !is_dirty && i < n/sizeof(long); i++)
+                is_dirty = memslot->dirty_bitmap[i];
 
         /* If nothing is dirty, don't bother messing with page tables. */
         if (is_dirty) {
+                struct kvm_memslots *slots, *old_slots;
+
                 spin_lock(&kvm->mmu_lock);
                 kvm_mmu_slot_remove_write_access(kvm, log->slot);
                 spin_unlock(&kvm->mmu_lock);
-                memslot = &kvm->memslots->memslots[log->slot];
-                n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
-                memset(memslot->dirty_bitmap, 0, n);
+
+                slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
+                if (!slots)
+                        goto out_free;
+
+                memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
+                slots->memslots[log->slot].dirty_bitmap = dirty_bitmap;
+
+                old_slots = kvm->memslots;
+                rcu_assign_pointer(kvm->memslots, slots);
+                synchronize_srcu_expedited(&kvm->srcu);
+                dirty_bitmap = old_slots->memslots[log->slot].dirty_bitmap;
+                kfree(old_slots);
         }
+
         r = 0;
+        if (copy_to_user(log->dirty_bitmap, dirty_bitmap, n))
+                r = -EFAULT;
+out_free:
+        vfree(dirty_bitmap);
 out:
         up_write(&kvm->slots_lock);
         return r;