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Date: Tue, 26 Jan 2010 16:02:32 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH] ide save/restore current transfer fields
References: <1264006909-22040-1-git-send-email-quintela@redhat.com>
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To: Juan Quintela <quintela@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org

On 01/20/2010 11:01 AM, Juan Quintela wrote:
> From: Marcelo Tosatti<mtosatti@redhat.com>
>
> If migration takes place between write of the bmdma address register and
> write of the command register (to initiate DMA), the destination will
> not properly start the DMA op, hanging the guest:
>
> ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
> ata1.00: cmd c8/00:16:41:00:00/00:00:00:00:00/e0 tag 0 dma 11264 in
>           res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
> ata1.00: status: { DRDY }
>
> Fix by sending current transfer information in the migration data.
>
> We need to update ide version to 4 for this to work.  As we don't
> have subsectios, we need to chain the update increase until
> vmstate_ide_pci (quintela)
>
> Signed-off-by: Marcelo Tosatti<mtosatti@redhat.com>
> Signed-off-by: Juan Quintela<quintela@redhat.com>
>    

Applied.  Thanks.

This is one of those nasty stable situations.  If we backport to stable, 
we fix a potentially bug but we max migration within stable impossible.  
We really ought to blacklist the old version too without an explicit 
override.

Any thoughts on how to handle this?  We at least have to record this as 
an issue.

Regards,

Anthony Liguori