Re: [PULL 18/38] Remove unnecessary minimum_version_id_old fields

From: Peter Maydell <peter.maydell@linaro.org>
To: Juan Quintela <quintela@redhat.com>
Cc: "Fam Zheng" <fam@euphon.net>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Jason Wang" <jasowang@redhat.com>,
	"Mark Cave-Ayland" <mark.cave-ayland@ilande.co.uk>,
	qemu-devel@nongnu.org, "Peter Xu" <peterx@redhat.com>,
	"Laurent Vivier" <Laurent@vivier.eu>,
	"Gerd Hoffmann" <kraxel@redhat.com>,
	"Ani Sinha" <ani@anisinha.ca>,
	"Edgar E. Iglesias" <edgar.iglesias@gmail.com>,
	"Eric Blake" <eblake@redhat.com>,
	"Hannes Reinecke" <hare@suse.com>,
	"Vikram Garhwal" <fnu.vikram@xilinx.com>,
	qemu-block@nongnu.org,
	"Daniel Henrique Barboza" <danielhb413@gmail.com>,
	"Markus Armbruster" <armbru@redhat.com>,
	"Artyom Tarasenko" <atar4qemu@gmail.com>,
	"Pavel Pisa" <pisa@cmp.felk.cvut.cz>,
	"Alistair Francis" <alistair@alistair23.me>,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	"Greg Kurz" <groug@kaod.org>,
	qemu-arm@nongnu.org, "Cédric Le Goater" <clg@kaod.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Stafford Horne" <shorne@gmail.com>,
	"David Gibson" <david@gibson.dropbear.id.au>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	"Andrew Baumann" <Andrew.Baumann@microsoft.com>,
	qemu-ppc@nongnu.org, "Igor Mammedov" <imammedo@redhat.com>,
	"Aurelien Jarno" <aurelien@aurel32.net>
Subject: Re: [PULL 18/38] Remove unnecessary minimum_version_id_old fields
Date: Tue, 15 Feb 2022 17:13:42 +0000	[thread overview]
Message-ID: <CAFEAcA8+ri-ndQv0b10yfUjSJZwH5Ec08S10_-2k5C8_OMYYDg@mail.gmail.com> (raw)
In-Reply-To: <20220127150548.20595-19-quintela@redhat.com>

On Thu, 27 Jan 2022 at 15:14, Juan Quintela <quintela@redhat.com> wrote:
>
> From: Peter Maydell <peter.maydell@linaro.org>
>
> The migration code will not look at a VMStateDescription's
> minimum_version_id_old field unless that VMSD has set the
> load_state_old field to something non-NULL.  (The purpose of
> minimum_version_id_old is to specify what migration version is needed
> for the code in the function pointed to by load_state_old to be able
> to handle it on incoming migration.)
>
> We have exactly one VMSD which still has a load_state_old,
> in the PPC CPU; every other VMSD which sets minimum_version_id_old
> is doing so unnecessarily. Delete all the unnecessary ones.
>
> Commit created with:
>   sed -i '/\.minimum_version_id_old/d' $(git grep -l '\.minimum_version_id_old')
> with the one legitimate use then hand-edited back in.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Juan Quintela <quintela@redhat.com>
>
> Signed-off-by: Juan Quintela <quintela@redhat.com>
>
> ---
>
> It missed vmstate_ppc_cpu.

No, as the commit message notes, it deliberately did not change
that one vmstate, because at the time of writing the patch
that was the one vmstate that really was still using
load_state_old. As it happens commit 8f91aca7ff0044b hit
master first, removing that use of load_state_old (but
forgetting to remove the minimum_version_id_old field along
with it), so this commit as it hit master is OK.

-- PMM