Re: [Qemu-devel] [PATCH v2 1/3] migration: Read JSON VM description on incoming migration

[Dr. David Alan Gilbert]

* Alexander Graf (address@hidden) wrote:
> One of the really nice things about the VM description format is that it goes
> over the wire when live migration is happening. Unfortunately QEMU today 
> closes
> any socket once it sees VM_EOF coming, so we never give the VMDESC the chance 
> to
> actually land on the wire.
> 
> This patch makes QEMU read the description as well. This way we ensure that
> anything wire tapping us in between will get the chance to also interpret the
> stream.
> 
> Along the way we also fix virt tests that assume that number_bytes_sent on the
> sender side is equal to number_bytes_read which was true before the VMDESC
> patches and is true again with this patch.
> 
> Signed-off-by: Alexander Graf <address@hidden>

Reviewed-by: Dr. David Alan Gilbert <address@hidden>

and I've tested the set of 3 and it works, so:

Tested-by: Dr. David Alan Gilbert <address@hidden>

Dave

> 
> ---
> 
> v1 -> v2:
> 
>   - read in small chunks
> ---
>  savevm.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/savevm.c b/savevm.c
> index 8040766..1b78654 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -929,6 +929,7 @@ int qemu_loadvm_state(QEMUFile *f)
>      uint8_t section_type;
>      unsigned int v;
>      int ret;
> +    int file_error_after_eof = -1;
>  
>      if (qemu_savevm_state_blocked(&local_err)) {
>          error_report("%s", error_get_pretty(local_err));
> @@ -1034,6 +1035,24 @@ int qemu_loadvm_state(QEMUFile *f)
>          }
>      }
>  
> +    file_error_after_eof = qemu_file_get_error(f);
> +
> +    /*
> +     * Try to read in the VMDESC section as well, so that dumping tools that
> +     * intercept our migration stream have the chance to see it.
> +     */
> +    if (qemu_get_byte(f) == QEMU_VM_VMDESCRIPTION) {
> +        uint32_t size = qemu_get_be32(f);
> +        uint8_t *buf = g_malloc(0x1000);
> +
> +        while (size > 0) {
> +            uint32_t read_chunk = MIN(size, 0x1000);
> +            qemu_get_buffer(f, buf, read_chunk);
> +            size -= read_chunk;
> +        }
> +        g_free(buf);
> +    }
> +
>      cpu_synchronize_all_post_init();
>  
>      ret = 0;
> @@ -1045,7 +1064,8 @@ out:
>      }
>  
>      if (ret == 0) {
> -        ret = qemu_file_get_error(f);
> +        /* We may not have a VMDESC section, so ignore relative errors */
> +        ret = file_error_after_eof;
>      }
>  
>      return ret;
> -- 
> 1.7.12.4
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK