Re: [Qemu-devel] [PATCH] migration: introduce decompress-error-check

[Peter Xu <peterx@redhat.com>]

On Fri, Apr 27, 2018 at 11:15:37AM +0800, Xiao Guangrong wrote:
> 
> 
> On 04/26/2018 10:01 PM, Eric Blake wrote:
> > On 04/26/2018 04:15 AM, guangrong.xiao@gmail.com wrote:
> > > From: Xiao Guangrong <xiaoguangrong@tencent.com>
> > > 
> > > QEMU 2.13 enables strict check for compression & decompression to
> > > make the migration more robuster, that depends on the source to fix
> > 
> > s/robuster/robust/
> > 
> 
> Will fix, thank you for pointing it out.
> 
> > > the internal design which triggers the unexpected error conditions
> > 
> > 2.13 hasn't been released yet.  Why do we need a knob to explicitly turn
> > off strict checking?  Can we not instead make 2.13 automatically smart
> > enough to tell if the incoming stream is coming from an older qemu
> > (which might fail if the strict checks are enabled) vs. a newer qemu
> > (the sender gave us what we need to ensure the strict checks are
> > worthwhile)?
> > 
> 
> Really smart.
> 
> How about introduce a new command, MIG_CMD_DECOMPRESS_ERR_CHECK,
> the destination will do strict check if got this command (i.e, new
> QEMU is running on the source), otherwise, turn the check off.

Why not we just introduce a compat bit for that?  I mean something
like: 15c3850325 ("migration: move skip_section_footers",
2017-06-28).  Then we turn that check bit off for <=2.12.

Would that work?

(I would suspect that's what Eric mean too)

Regards,

-- 
Peter Xu