Messages in this thread | | | Date | Tue, 11 Dec 2012 23:29:09 -0200 | From | Marcelo Tosatti <> | Subject | Re: [PATCH v2 01/10] kvm: Restrict non-existing slot state transitions |
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On Mon, Dec 10, 2012 at 10:32:45AM -0700, Alex Williamson wrote: > 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. > > Signed-off-by: Alex Williamson <alex.williamson@redhat.com> > --- > virt/kvm/kvm_main.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 6e8fa7e..e426704 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -753,10 +753,15 @@ 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;
/* General sanity checks */ if (mem->memory_size & (PAGE_SIZE - 1)) goto out; if (mem->guest_phys_addr & (PAGE_SIZE - 1)) goto out;
if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr) goto out;
If mem->memory_size is zero, then check above fails. If mem->memory_size > 0, it must be at least PAGE_SIZE, in which case npages == 1.
Which means the code does not allow changes to non-existing slots. Yes?
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