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Subject: [Qemu-devel] Re: [PATCH v2 2/6] Introduce bit-based phys_ram_dirty
 for VGA, CODE, MIGRATION and MASTER.
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To: Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>
Cc: aliguori@us.ibm.com, kvm@vger.kernel.org, ohmura.kei@lab.ntt.co.jp, mtosatti@redhat.com, qemu-devel@nongnu.org

On 04/12/2010 12:39 PM, Yoshiaki Tamura wrote:
>> Please put in some header file, maybe qemu-common.h.
>
>
> OK.  BTW, is qemu-kvm.h planned to go upstream?

No.  Use kvm.h for kvm specific symbols (qemu-kvm.h includes it).

>>
>> Should be nicer as a loop calling a helper to allocate each bitmap. This
>> patch won't work by itself, will it? I think you need to merge it with
>> the succeeding patches.
>
> Yeah.  I originally wrote as you suggested, but I needed to skip 0x03 
> because of the reason written below.
>
>> +/* Use DIRTY_FLAG as indexes of bit-based phys_ram_dirty.
>> +   0x03 is empty to make it compatible with byte-based bitmap. */
>> +#define MASTER_DIRTY_FLAG    0x00
>>  #define VGA_DIRTY_FLAG       0x01
>>  #define CODE_DIRTY_FLAG      0x02
>> -#define MIGRATION_DIRTY_FLAG 0x08
>> +#define MIGRATION_DIRTY_FLAG 0x04
>
> If you think if (i != 0x03) is better, I would modify it to a loop.

You can have *_DIRTY_FLAG (1, 2, 4, 8) and *_DIRTY_IDX (0, 1, 2, 3); use 
_FLAG for compatibility with byte-based maps, and _IDX for multiple bitmaps.

Alternatively, have only _IDX, and modify the callers to shift when 
necessary.  At the end of the patchset, we'll only use bitmaps, so the 
shifts will be all gone.


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.