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KVM: Restrict non-existing slot state transitions 

The API documentation states:

	When changing an existing slot, it may be moved in the guest
	physical memory space, or its flags may be modified.

An "existing slot" requires a non-zero npages (memory_size).  The only
transition we should therefore allow for a non-existing slot should be
to create the slot, which includes setting a non-zero memory_size.  We
currently allow calls to modify non-existing slots, which is pointless,
confusing, and possibly wrong.

With this we know that the invalidation path of __kvm_set_memory_region
is always for a delete or move and never for adding a zero size slot.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Alex Williamson 2012-12-10 10:32:45 -07:00 committed by Marcelo Tosatti
parent f3200d00ea
commit f0736cf055
1 changed files with 7 additions and 2 deletions
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9
virt/kvm/kvm_main.c
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@ -758,10 +758,15 @@ int __kvm_set_memory_region(struct kvm *kvm,
new.npages = npages;
new.flags = mem->flags;
/* Disallow changing a memory slot's size. */
/*
* Disallow changing a memory slot's size or changing anything about
* zero sized slots that doesn't involve making them non-zero.
*/
r = -EINVAL;
if (npages && old.npages && npages != old.npages)
goto out_free;
if (!npages && !old.npages)
goto out_free;
/* Check for overlaps */
r = -EEXIST;
@ -780,7 +785,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
r = -ENOMEM;
/* Allocate if a slot is being created */
if (npages && !old.npages) {
if (!old.npages) {
new.user_alloc = user_alloc;
new.userspace_addr = mem->userspace_addr;