Re: [PATCH] kvm: coalesced_mmio: remove one redundant check inside of coalesced_mmio_in_range()

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

On 2014/12/11 19:29, Paolo Bonzini wrote:
>
>
> On 11/12/2014 04:02, Tiejun Chen wrote:
>> We already check 'len' above to make sure it already isn't
>> negative here, so indeed, (addr + len < addr) should never be happened.
>
> ... except if there is an overflow.

Sorry, I'm confused. 'addr' is u64 and now 'len' would always be '>=0', 
what's your a so-called overflow here? And we also have such a check 
below, (addr + len > dev->zone.addr + dev->zone.size), so can this 
guarantee an overflow?

Thanks
Tiejun

>
> Paolo
>
>> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
>> ---
>>   virt/kvm/coalesced_mmio.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
>> index 00d8642..60f59cd 100644
>> --- a/virt/kvm/coalesced_mmio.c
>> +++ b/virt/kvm/coalesced_mmio.c
>> @@ -30,8 +30,6 @@ static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
>>   	 */
>>   	if (len < 0)
>>   		return 0;
>> -	if (addr + len < addr)
>> -		return 0;
>>   	if (addr < dev->zone.addr)
>>   		return 0;
>>   	if (addr + len > dev->zone.addr + dev->zone.size)
>>
> --
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