x86/vcpu: relax VCPUOP_initialise restriction for non-PV vCPUs

There's no reason to force HVM guests to have a valid vcpu_info area when
initializing a vCPU, as the vCPU can also be brought online using the local
APIC, and on that path there's no requirement for vcpu_info to be setup ahead
of the bring up.  Note an HVM vCPU can operate normally without making use of
vcpu_info, and in fact does so when brought up via the local APIC.

Restrict the check against dummy_vcpu_info to only apply to PV guests.

Fixes: 192df6f912 ('x86: allow HVM guests to use hypercalls to bring up vCPUs')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/common/compat/domain.c

@@ -49,7 +49,7 @@ int compat_common_vcpu_op(int cmd, struct vcpu *v,
     {
     case VCPUOP_initialise:
     {
-        if ( v->vcpu_info_area.map == &dummy_vcpu_info )
+        if ( is_pv_domain(d) && v->vcpu_info_area.map == &dummy_vcpu_info )
             return -EINVAL;
 
 #ifdef CONFIG_HVM

xen/common/domain.c

@@ -1827,7 +1827,7 @@ long common_vcpu_op(int cmd, struct vcpu *v, XEN_GUEST_HANDLE_PARAM(void) arg)
     switch ( cmd )
     {
     case VCPUOP_initialise:
-        if ( v->vcpu_info_area.map == &dummy_vcpu_info )
+        if ( is_pv_domain(d) && v->vcpu_info_area.map == &dummy_vcpu_info )
             return -EINVAL;
 
         rc = arch_initialise_vcpu(v, arg);