Commit f0736cf0 authored Dec 10, 2012 by Alex Williamson Committed by Marcelo Tosatti Dec 13, 2012

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>

parent f3200d00

virt/kvm/kvm_main.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -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;

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