Re: [RFC PATCH 5/6] kvm: Re-introduce memslots->nmemslots

[Alex Williamson]

On Thu, 2012-12-06 at 21:59 -0200, Marcelo Tosatti wrote:
> On Thu, Dec 06, 2012 at 09:58:48PM -0200, Marcelo Tosatti wrote:
> > On Wed, Dec 05, 2012 at 08:51:37PM -0700, Alex Williamson wrote:
> > > > > id_to_memslot seems like a good place to catch all the users since
> > > > > that's the only way to get a slot from a slot id after the array is
> > > > > sorted.  We need to check both is the slot in bounds (EINVAL), but also
> > > > > is it allocated (ENOENT).  id_to_memslot could both of these if we
> > > > > wanted to switch it to ERR_PTR.  Thanks,
> > > > > 
> > > > > Alex
> > > > 
> > > > There should never be a reference to a slot out of bounds by KVM itself
> > > > (BUG_ON). Only userspace can attempt a reference to such slot.
> > > 
> > > If I understand correctly, you're saying this last chunk is unique
> > > because kvm_get_dirty_log() is an internal interface and the test should
> > > be restricted to callers from userspace interfaces, namely
> > > kvm_vm_ioctl_get_dirty_log().  That sounds reasonable; book3s_pr seems
> > > to be the only caller that relies on kvm_get_dirty_log() validating the
> > > slot.  Thanks,
> > > 
> > > Alex
> > 
> > Yep - so you can move the check to such userspace interfaces, and bug on 
> > on WARN otherwise (in id_to_memslot).
> 
> WARN_ON. The point is, if its not a valid condition, it should be
> explicitly so.
> 
> > Does that make sense??

Yep, I'll add that if we decide to go that route.  This patch isn't
necessary with the series I just posted since the array is still static.
Thanks,

Alex


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