Re: [Xen-devel] [PATCH v6] tools/migrate: Fix regression when migrating from older version of Xen

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-09-26 at 18:15 +0100, Andrew Cooper wrote:
> Commit 00a4b65f8534c9e6521eab2e6ce796ae36037774 Sep 7 2010
>   "libxc: provide notification of final checkpoint to restore end"
> broke migration from any version of Xen using tools from prior to that commit
> 
> Older tools have no idea about an XC_SAVE_ID_LAST_CHECKPOINT, causing newer
> tools xc_domain_restore() to start reading the qemu save record, as
> ctx->last_checkpoint is 0.
> 
> The failure looks like:
>   xc: error: Max batch size exceeded (1970103633). Giving up.
> where 1970103633 = 0x756d6551 = *(uint32_t*)"Qemu"
> 
> With this fix in place, the behaviour for normal migrations is reverted to how
> it was before the regression; the migration is considered non-checkpointed
> right from the start.  A XC_SAVE_ID_LAST_CHECKPOINT chunk seen in the
> migration stream is a nop.  For checkpointed migrations the behaviour is
> unchanged.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> CC: Shriram Rajagopalan <rshriram@xxxxxxxxx>

Shriram -- are you OK with the remusy bits of this?

> diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
> index 4cab294..7f8edd2 100644
> --- a/tools/libxl/libxl.h
> +++ b/tools/libxl/libxl.h
> @@ -355,6 +355,14 @@
>   */
>  #define LIBXL_HAVE_SPICE_VDAGENT 1
>  
> +/*
> + * LIBXL_HAVE_DOMAIN_CREATE_RESTORE_FLAGS 1
> + *
> + * If this is defined, libxl_domain_create_restore()'s API has changed to
> + * include a flags structure.
> + */
> +#define LIBXL_HAVE_DOMAIN_CREATE_RESTORE_FLAGS 1

flags isn't going to be right if we add e.g. rate limiting controls or
something. Lets go with "..._params".

> +
>  /* Functions annotated with LIBXL_EXTERNAL_CALLERS_ONLY may not be
>   * called from within libxl itself. Callers outside libxl, who
>   * do not #include libxl_internal.h, are fine. */
> @@ -578,9 +586,31 @@ int libxl_domain_create_new(libxl_ctx *ctx, 
> libxl_domain_config *d_config,
>                              LIBXL_EXTERNAL_CALLERS_ONLY;
>  int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config 
> *d_config,
>                                  uint32_t *domid, int restore_fd,
> +                                const libxl_domain_restore_flags *flags,
>                                  const libxl_asyncop_how *ao_how,
>                                  const libxl_asyncprogress_how 
> *aop_console_how)
>                                  LIBXL_EXTERNAL_CALLERS_ONLY;
> +
> +#if LIBXL_API_VERSION == 0x040200 || LIBXL_API_VERSION == 0x040300

#if LIBXL_API_VERSION <= 0x040300 please

> +
> +int static inline libxl_domain_create_restore_0x040200(
> +    libxl_ctx *ctx, libxl_domain_config *d_config,
> +    uint32_t *domid, int restore_fd,
> +    const libxl_asyncop_how *ao_how,
> +    const libxl_asyncprogress_how *aop_console_how)
> +    LIBXL_EXTERNAL_CALLERS_ONLY
> +{
> +    libxl_domain_restore_flags flags;
> +    flags.checkpointed_stream = 0;
> +
> +    return libxl_domain_create_restore(
> +        ctx, d_config, domid, restore_fd, &flags, ao_how, aop_console_how);
> +}
> +
> +#define libxl_domain_create_restore libxl_domain_create_restore_0x040200

This all looks good.

...So does the rest.

Ian.


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