Re: [PATCH v13 1/6] migrate: Skeleton of live migration logic

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, Feb 09, 2025 at 11:20:00PM +0100, Stefano Brivio wrote:
> Introduce facilities for guest migration on top of vhost-user
> infrastructure.  Add migration facilities based on top of the current
> vhost-user infrastructure, moving vu_migrate() and related functions
> to migrate.c.
> 
> Versioned migration stages define function pointers to be called on
> source or target, or data sections that need to be transferred.
> 
> The migration header consists of a magic number, a version number for the
> encoding, and a "compat_version" which represents the oldest version which
> is compatible with the current one.  We don't use it yet, but that allows
> for the future possibility of backwards compatible protocol extensions.
> 
> Co-authored-by: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

with the exception of one nit, which I hope to send a fixup patch for today:

[snip]

> +/**
> + * struct migrate_stage - Callbacks and parameters for one stage of migration
> + * @name:	Stage name (for debugging)
> + * @source:	Callback to implement this stage on the source
> + * @target:	Callback to implement this stage on the target
> + * @iov:	Optional data section to transfer
> + */
> +struct migrate_stage {
> +	const char *name;
> +	int (*source)(struct ctx *c, const struct migrate_stage *stage, int fd);
> +	int (*target)(struct ctx *c, const struct migrate_stage *stage, int fd);
> +
> +	/* Add here separate rollback callbacks if needed */
> +
> +	struct iovec iov;

We're no longer using this @iov field, and it can be removed.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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