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From: Xiao Guangrong <guangrong.xiao@gmail.com>
To: Peter Xu <peterx@redhat.com>
Cc: kvm@vger.kernel.org, mst@redhat.com, mtosatti@redhat.com,
	Xiao Guangrong <xiaoguangrong@tencent.com>,
	qemu-devel@nongnu.org, dgilbert@redhat.com, wei.w.wang@intel.com,
	jiang.biao2@zte.com.cn, pbonzini@redhat.com
Subject: Re: [PATCH] migration: introduce decompress-error-check
Date: Fri, 27 Apr 2018 18:40:09 +0800	[thread overview]
Message-ID: <2f84ab90-2b9c-9888-e6e2-9114ae046078@gmail.com> (raw)
In-Reply-To: <20180427093135.GC13269@xz-mi>



On 04/27/2018 05:31 PM, Peter Xu wrote:
> 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 am afraid it can not. :(

The compat bit only impacts local behavior, however, in this case, we
need the source QEMU to tell the destination if it supports strict
error check.

WARNING: multiple messages have this Message-ID
From: Xiao Guangrong <guangrong.xiao@gmail.com>
To: Peter Xu <peterx@redhat.com>
Cc: Eric Blake <eblake@redhat.com>,
	pbonzini@redhat.com, mst@redhat.com, mtosatti@redhat.com,
	kvm@vger.kernel.org, Xiao Guangrong <xiaoguangrong@tencent.com>,
	qemu-devel@nongnu.org, dgilbert@redhat.com, wei.w.wang@intel.com,
	jiang.biao2@zte.com.cn
Subject: Re: [Qemu-devel] [PATCH] migration: introduce decompress-error-check
Date: Fri, 27 Apr 2018 18:40:09 +0800	[thread overview]
Message-ID: <2f84ab90-2b9c-9888-e6e2-9114ae046078@gmail.com> (raw)
In-Reply-To: <20180427093135.GC13269@xz-mi>



On 04/27/2018 05:31 PM, Peter Xu wrote:
> 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 am afraid it can not. :(

The compat bit only impacts local behavior, however, in this case, we
need the source QEMU to tell the destination if it supports strict
error check.

  reply	other threads:[~2018-04-27 10:40 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-26  9:15 [PATCH] migration: introduce decompress-error-check guangrong.xiao
2018-04-26  9:15 ` [Qemu-devel] " guangrong.xiao
2018-04-26  9:19 ` Xiao Guangrong
2018-04-26  9:19   ` [Qemu-devel] " Xiao Guangrong
2018-04-26  9:34 ` Dr. David Alan Gilbert
2018-04-26  9:34   ` [Qemu-devel] " Dr. David Alan Gilbert
2018-04-26 13:18   ` Xiao Guangrong
2018-04-26 13:18     ` [Qemu-devel] " Xiao Guangrong
2018-04-26 14:01 ` Eric Blake
2018-04-26 14:01   ` [Qemu-devel] " Eric Blake
2018-04-27  3:15   ` Xiao Guangrong
2018-04-27  3:15     ` [Qemu-devel] " Xiao Guangrong
2018-04-27  9:31     ` Peter Xu
2018-04-27  9:31       ` [Qemu-devel] " Peter Xu
2018-04-27 10:40       ` Xiao Guangrong [this message]
2018-04-27 10:40         ` Xiao Guangrong
2018-05-02  3:03         ` Peter Xu
2018-05-02  3:03           ` [Qemu-devel] " Peter Xu
2018-05-02 14:57           ` Dr. David Alan Gilbert
2018-05-02 14:57             ` [Qemu-devel] " Dr. David Alan Gilbert
2018-05-03  2:10             ` Peter Xu
2018-05-03  2:10               ` [Qemu-devel] " Peter Xu
2018-04-27 11:29     ` Dr. David Alan Gilbert
2018-04-27 11:29       ` [Qemu-devel] " Dr. David Alan Gilbert
2018-04-28  6:13       ` Xiao Guangrong
2018-04-28  6:13         ` [Qemu-devel] " Xiao Guangrong

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