[PATCH for-4.15 1/2] xen/dmop: Fix XEN_DMOP_nr_vcpus to actually return data

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The const_op boolean needs clobbering to cause data to be written back to the
caller.

Fixes: c4441ab1f1 ("dmop: Add XEN_DMOP_nr_vcpus")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
---
 xen/arch/arm/dm.c     | 1 +
 xen/arch/x86/hvm/dm.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/xen/arch/arm/dm.c b/xen/arch/arm/dm.c
index d689e336fd..1b3fd6bc7d 100644
--- a/xen/arch/arm/dm.c
+++ b/xen/arch/arm/dm.c
@@ -128,6 +128,7 @@ int dm_op(const struct dmop_args *op_args)
         struct xen_dm_op_nr_vcpus *data = &op.u.nr_vcpus;
 
         data->vcpus = d->max_vcpus;
+        const_op = false;
         rc = 0;
         break;
     }
diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
index f4f0910463..b60b9f3364 100644
--- a/xen/arch/x86/hvm/dm.c
+++ b/xen/arch/x86/hvm/dm.c
@@ -612,6 +612,7 @@ int dm_op(const struct dmop_args *op_args)
         struct xen_dm_op_nr_vcpus *data = &op.u.nr_vcpus;
 
         data->vcpus = d->max_vcpus;
+        const_op = false;
         rc = 0;
         break;
     }
-- 
2.11.0