Re: [PATCH v1 COLO Pre 02/12] libxc/restore: zero ioreq page only one time

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 02/06/15 10:26, Yang Hongyang wrote:
> ioreq page contains evtchn which will be set when we resume the
> secondary vm the first time. The hypervisor will check if the
> evtchn is corrupted, so we cannot zero the ioreq page more
> than one time.
>
> The ioreq->state is always STATE_IOREQ_NONE after the vm is
> suspended, so it is OK if we only zero it one time.
>
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> Signed-off-by: Wen congyang <wency@cn.fujitsu.com>
> CC: Andrew Cooper <andrew.cooper3@citrix.com>

Is the qemu process for the secondary running at this point?  If so,
this is very much unsafe.

~Andrew

> ---
>  tools/libxc/xc_sr_restore_x86_hvm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/libxc/xc_sr_restore_x86_hvm.c b/tools/libxc/xc_sr_restore_x86_hvm.c
> index 6f5af0e..06177e0 100644
> --- a/tools/libxc/xc_sr_restore_x86_hvm.c
> +++ b/tools/libxc/xc_sr_restore_x86_hvm.c
> @@ -78,7 +78,8 @@ static int handle_hvm_params(struct xc_sr_context *ctx,
>              break;
>          case HVM_PARAM_IOREQ_PFN:
>          case HVM_PARAM_BUFIOREQ_PFN:
> -            xc_clear_domain_page(xch, ctx->domid, entry->value);
> +            if ( !ctx->restore.buffer_all_records )
> +                xc_clear_domain_page(xch, ctx->domid, entry->value);
>              break;
>          }
>