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@xxxxxxxxx>
>>> ---
>>> 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,
((1ULL << (-1 + 1)) - 1) << s
> = (1ULL << (0) - 1) << s
((1ULL << (0)) - 1) << s
> = (1ULL << (- 1) << s
(1 - 1) << s
0 << s
Paolo
>
> Am I missing something?
>
> Thanks
> Tiejun
>
>> (1ULL << 0) << s ==
>> 0
>>
>> Is there any case where s is even bigger?
>>
>> Paolo
>> --
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