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Date: Wed, 08 Aug 2018 09:30:42 +0800
From: Wei Wang <wei.w.wang@intel.com>
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Subject: Re: [Qemu-devel] [PATCH v2] bitmap: fix BITMAP_LAST_WORD_MASK
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To: Peter Xu <peterx@redhat.com>
Cc: qemu-devel@nongnu.org, dgilbert@redhat.com, quintela@redhat.com, mst@redhat.com

On 08/07/2018 08:17 PM, Peter Xu wrote:
> On Tue, Aug 07, 2018 at 04:21:15PM +0800, Wei Wang wrote:
>> On 08/07/2018 03:39 PM, Peter Xu wrote:
>>> On Tue, Jul 31, 2018 at 06:01:18PM +0800, Wei Wang wrote:
>>>> When "nbits = 0", which means no bits to mask, this macro is expected to
>>>> return 0, instead of 0xffffffff. This patch changes the macro to return
>>>> 0 when there is no bit needs to be masked.
>>>>
>>>> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
>>>> CC: Juan Quintela <quintela@redhat.com>
>>>> CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>> CC: Peter Xu <peterx@redhat.com>
>>> Reviewed-by: Peter Xu <peterx@redhat.com>
>>>
>>> Is there any existing path that can trigger this nbits==0?
>> Not sure about other bitmap APIs which call this macro. But it happens in
>> the patches we are working on, which use bitmap_count_one.
>> It would be good to have the macro itself handle this corner case, so that
>> callers won't need to worry about that.
> Yeah that makes sense.  Asked since that would matter on whether it's
> 3.0 material, then it's possibly not.
>

OK, thanks for checking.

Best,
Wei