On Tue, 2012-12-11 at 23:39 -0200, Marcelo Tosatti wrote: > On Tue, Dec 11, 2012 at 11:29:09PM -0200, Marcelo Tosatti wrote: > > 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.william...@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. > > Err, no read a "<=" while writing that.
;) Thanks for the double check, Alex > > 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? > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
