Re: [Qemu-devel] [PATCH] migration: fix incorrect enable return path

[Laurent Vivier <lvivier@redhat.com>]

On 14/06/2017 09:55, Peter Xu wrote:
> 0425dc9 is actually v1 of that patch, but it was accidentally
> merged (while there was a v2). That will cause problem when we try to
> migrate to some old QEMUs when return path is not really there. Let's
> fix it, then squashing this patch with 0425dc9 will be exactly patch
> content of v2.
> 
> Fixes: 0425dc9 ("migration: isolate return path on src")
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  migration/migration.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 8ef6d6c..f9053b0 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1814,7 +1814,11 @@ static void *migration_thread(void *opaque)
>  
>      qemu_savevm_state_header(s->to_dst_file);
>  
> -    if (s->to_dst_file) {
> +    /*
> +     * If we opened the return path, we need to make sure dst has it
> +     * opened as well.
> +     */
> +    if (s->rp_state.from_dst_file) {
>          /* Now tell the dest that it should open its end so it can reply */
>          qemu_savevm_send_open_return_path(s->to_dst_file);
>  
> 

Tested-by: Laurent Vivier <lvivier@redhat.com>

This also fixes migration of pseries guest, using the same
binary/machine type on both side, the error was:

qemu-system-ppc64: Failed to load spapr_iommu:mig_table
qemu-system-ppc64: error while loading state for instance 0x80000001 of
device 'spapr_iommu'
qemu-system-ppc64: load of migration failed: Input/output error

Laurent