Re: [PATCH V2] migration: file URI

[Daniel P . Berrangé]

On Wed, Jun 07, 2023 at 11:38:59AM -0700, Steve Sistare wrote:
> Extend the migration URI to support file:<filename>.  This can be used for
> any migration scenario that does not require a reverse path.  It can be used
> as an alternative to 'exec:cat > file' in minimized containers that do not
> contain /bin/sh, and it is easier to use than the fd:<fdname> URI.  It can
> be used in HMP commands, and as a qemu command-line parameter.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>

> diff --git a/qemu-options.hx b/qemu-options.hx
> index b37eb96..b93449d 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -4610,6 +4610,7 @@ DEF("incoming", HAS_ARG, QEMU_OPTION_incoming, \
>      "                prepare for incoming migration, listen on\n" \
>      "                specified protocol and socket address\n" \
>      "-incoming fd:fd\n" \
> +    "-incoming file:filename\n" \
>      "-incoming exec:cmdline\n" \
>      "                accept incoming migration on given file descriptor\n" \
>      "                or from given external command\n" \
> @@ -4626,7 +4627,10 @@ SRST
>      Prepare for incoming migration, listen on a given unix socket.
>  
>  ``-incoming fd:fd``
> -    Accept incoming migration from a given filedescriptor.
> +    Accept incoming migration from a given file descriptor.
> +
> +``-incoming file:filename``
> +    Accept incoming migration from a given file.

To be usable for libvirt we need to support an offset

   -incoming file:filename,offset=NNNN

because for save/restore to disk,libvirt stores its own header and XML
document in front of the QEMU save state, and we need to be able to
tell QEMU to leave space (on save) or skip over it (on restore).

With regards,
Daniel
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