Re: [Qemu-devel] [PATCH] migratioin/ram: leave RAMBlock->bmap blank on allocating

[Wei Yang]

On Mon, Jun 03, 2019 at 02:05:47PM +0800, Wei Yang wrote:
>On Mon, Jun 03, 2019 at 01:40:13PM +0800, Peter Xu wrote:
>>
>>Ah I see, thanks for the pointer.  Then I would agree it's fine.
>>
>>I'm not an expert of TCG - I'm curious on why all those three dirty
>>bitmaps need to be set at the very beginning.  IIUC at least the VGA
>>bitmap should not require that (so IMHO we should be fine to have all
>>zeros with VGA bitmap for ramblocks, and we only set them when the
>>guest touches them).  Migration bitmap should be special somehow but I
>>don't know much on TCG/TLB part I'd confess so I can't say.  In other
>>words, if migration is the only one that requires this "all-1"
>>initialization then IMHO we may consider to remove the other part
>>rather than here in migration because that's what we'd better to be
>>sure with.
>
>I am not sure about the background here, so I didn't make a change at this
>place.
>
>>
>>And even if you want to remove this, I still have two suggestions:
>>
>>(1) proper comment here above bmap on the above fact that although
>>    bmap is not set here but it's actually set somewhere else because
>>    we'll sooner or later copy all 1s from the ramblock bitmap
>>
>>(2) imho you can move "migration_dirty_pages = 0" into
>>    ram_list_init_bitmaps() too to let them be together
>>

I took a look into this one.

ram_list_init_bitmaps() setup bitmap for each RAMBlock, while ram_state_init()
setup RAMState. Since migration_dirty_pages belongs to RAMState, it maybe more
proper to leave it at the original place.

Do you feel good about this?

>
>I will address these two comments and send v2.
>
>Thanks.
>
>>-- 
>>Peter Xu
>
>-- 
>Wei Yang
>Help you, Help me

-- 
Wei Yang
Help you, Help me