Re: [RFC][PATCH 1/2] kvm: x86: mmu: return zero if s > e in rsvd_bits()

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2014/11/17 17:22, Paolo Bonzini wrote:
>
>
> On 17/11/2014 02:34, Chen, Tiejun wrote:
>> On 2014/11/14 18:06, Paolo Bonzini wrote:
>>>
>>>
>>> On 14/11/2014 10:31, Tiejun Chen wrote:
>>>> In some real scenarios 'start' may not be less than 'end' like
>>>> maxphyaddr = 52.
>>>>
>>>> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
>>>> ---
>>>>    arch/x86/kvm/mmu.h | 2 ++
>>>>    1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
>>>> index bde8ee7..0e98b5e 100644
>>>> --- a/arch/x86/kvm/mmu.h
>>>> +++ b/arch/x86/kvm/mmu.h
>>>> @@ -58,6 +58,8 @@
>>>>
>>>>    static inline u64 rsvd_bits(int s, int e)
>>>>    {
>>>> +    if (unlikely(s > e))
>>>> +        return 0;
>>>>        return ((1ULL << (e - s + 1)) - 1) << s;
>>>>    }
>>>>
>>>>
>>>
>>> s == e + 1 is supported:
>>>
>>>      (1ULL << (e - (e + 1) + 1)) - 1) << s ==
>>
>> (1ULL << (e - (e + 1) + 1)) - 1) << s
>>      = (1ULL << (e - e - 1) + 1)) - 1) << s
>>      = (1ULL << (-1) + 1)) - 1) << s
>
> no,

You're right since I'm seeing "()" wrongly.

Sorry to bother you.

Thanks
Tiejun