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Thu, 18 May 2023 16:51:36 +0000 Received: from DM6PR12MB5549.namprd12.prod.outlook.com ([fe80::a29a:c3cf:5edf:9dad]) by DM6PR12MB5549.namprd12.prod.outlook.com ([fe80::a29a:c3cf:5edf:9dad%7]) with mapi id 15.20.6411.017; Thu, 18 May 2023 16:51:36 +0000 Message-ID: Date: Thu, 18 May 2023 19:51:27 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 Subject: Re: [PATCH v2 3/7] migration: Enable precopy initial data capability Content-Language: en-US To: Peter Xu Cc: qemu-devel@nongnu.org, Alex Williamson , =?UTF-8?Q?C=c3=a9dric_Le_Goater?= , Eduardo Habkost , Marcel Apfelbaum , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Yanan Wang , Juan Quintela , Leonardo Bras , Eric Blake , Markus Armbruster , Thomas Huth , Laurent Vivier , Paolo Bonzini , Yishai Hadas , Jason Gunthorpe , Maor Gottlieb , Kirti Wankhede , Tarun Gupta , Joao Martins References: <20230517155219.10691-1-avihaih@nvidia.com> <20230517155219.10691-4-avihaih@nvidia.com> From: Avihai Horon In-Reply-To: Content-Type: text/plain; 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envelope-from=avihaih@nvidia.com; helo=NAM12-BN8-obe.outbound.protection.outlook.com X-Spam_score_int: -46 X-Spam_score: -4.7 X-Spam_bar: ---- X-Spam_report: (-4.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-2.544, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 18/05/2023 16:42, Peter Xu wrote: > External email: Use caution opening links or attachments > > > On Thu, May 18, 2023 at 10:26:04AM +0300, Avihai Horon wrote: >> On 17/05/2023 19:07, Peter Xu wrote: >>> External email: Use caution opening links or attachments >>> >>> >>> On Wed, May 17, 2023 at 06:52:15PM +0300, Avihai Horon wrote: >>>> Now that precopy initial data logic has been implemented, enable the >>>> capability. >>>> >>>> Signed-off-by: Avihai Horon >>>> Reviewed-by: Juan Quintela >>>> --- >>>> migration/options.c | 4 ---- >>>> 1 file changed, 4 deletions(-) >>>> >>>> diff --git a/migration/options.c b/migration/options.c >>>> index 0a31921a7a..3449ce4f14 100644 >>>> --- a/migration/options.c >>>> +++ b/migration/options.c >>>> @@ -561,10 +561,6 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp) >>>> "capability 'return-path'"); >>>> return false; >>>> } >>>> - >>>> - /* Disable this capability until it's implemented */ >>>> - error_setg(errp, "'precopy-initial-data' is not implemented yet"); >>>> - return false; >>>> } >>> I'm always confused why we need this and not having this squashed into >>> patch 1 (or say, never have these lines). >>> >>> The only thing it matters is when someone backports patch 1 but not >>> backport the rest of the patches. But that's really, really weird already >>> as a backporter doing that, and I doubt its happening. >>> >>> Neither should we merge patch 1 without merging follow up patches to >>> master, as we should just always merge the whole feature or just keep >>> reworking on the list. >>> >>> I'd like to know if I missed something else.. >> There are also git bisect considerations. >> This practice is useful for git bisect for features that are enabled by >> default, so you won't mistakenly run "half a feature" if you do bisect. >> But here the capability must be manually enabled, so maybe it's not that >> useful in this case. >> >> I like it for the sake of good order, so this capability can't be enabled >> before it's fully implemented (even if it's unlikely that someone would do >> that). > Right. I was kind of thinking someone bisecting such feature will always > make sure to start from the last commit got merged, but I see your point as > a general concept. > > One slightly better way to not add something and remove again is, we can > introduce migrate_precopy_initial_data() in patch 2, returning constantly > false, then we can put patch 1 (qapi interface) to be after current patch > 2, where you allow migrate_precopy_initial_data() to start return true. It > saves a few lines to remove, and also one specific patch explicitly > removing it. But I think fundamentally it's similar indeed. > > In case you'd like to keep this as is, feel free to add: > > Reviewed-by: Peter Xu I think I will keep it as is, it seems more natural to me. However, if someone insists then I don't mind changing it. Thanks!