[PATCH] x86/domain: adjust limitation on shared_info allocation below 4G

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

The limitation of shared_info being allocated below 4G to fit in the
start_info field only applies to 32bit PV guests.  On 64bit PV guests the
start_info field is 64bits wide.  HVM guests don't use start_info at all.

Limit the allocation address restriction to 32bit PV guests only.

Fixes: 3cadc0469d5c ("x86_64: shared_info must be allocated below 4GB as it is 
advertised to 32-bit guests via a 32-bit machine address field in start_info.")
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/domain.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index edb76366b596..4163568043b1 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -882,10 +882,13 @@ int arch_domain_create(struct domain *d,
         goto fail;
 
     /*
-     * The shared_info machine address must fit in a 32-bit field within a
-     * 32-bit guest's start_info structure. Hence we specify MEMF_bits(32).
+     * For 32bit PV guests the shared_info machine address must fit in a 32-bit
+     * field within the guest's start_info structure. Hence we specify
+     * MEMF_bits(32).
      */
-    if ( (d->shared_info = alloc_xenheap_pages(0, MEMF_bits(32))) == NULL )
+    if ( (d->shared_info =
+          alloc_xenheap_pages(0, is_pv_32bit_domain(d) ? MEMF_bits(32)
+                                                       : 0)) == NULL )
         goto fail;
 
     clear_page(d->shared_info);
-- 
2.51.0