Re: [PATCH v5 02/12] KVM: hide KVM_MEMSLOT_INVALID from userspace

[Marcelo Tosatti <mtosatti@redhat.com>]

On Tue, Aug 07, 2012 at 05:48:49PM +0800, Xiao Guangrong wrote:
> Quote Avi's comment:
> | KVM_MEMSLOT_INVALID is actually an internal symbol, not used by
> | userspace.  Please move it to kvm_host.h.
> 
> Also, move KVM_MEMSLOT_INVALID to the highest bit
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
> ---
>  include/linux/kvm.h      |    1 -
>  include/linux/kvm_host.h |    2 ++
>  2 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> index 2ce09aa..dc3aa2a 100644
> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -103,7 +103,6 @@ struct kvm_userspace_memory_region {
> 
>  /* for kvm_memory_region::flags */
>  #define KVM_MEM_LOG_DIRTY_PAGES  1UL
> -#define KVM_MEMSLOT_INVALID      (1UL << 1)
> 
>  /* for KVM_IRQ_LINE */
>  struct kvm_irq_level {
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index d2b897e..4c2da5a 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -35,6 +35,8 @@
>  #define KVM_MMIO_SIZE 8
>  #endif
> 
> +#define KVM_MEMSLOT_INVALID	(1UL << 31)
> +
>  /*
>   * If we support unaligned MMIO, at most one fragment will be split into two:
>   */

Please document which range is for userspace visible flags, which range
is reserved. Mention that in both headers, point to each other
("userspace definitions are there" / "internal definitions are there").

16/16 bits for each should be fine.