[PATCH V6 23/24] xen/ioreq: Do not let bufioreq to be used on other than x86 arches

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

This patch prevents the device model running on other than x86
systems to use buffered I/O feature for now.

Please note, there is no caller which requires to send buffered
I/O request on Arm currently and the purpose of this check is
to catch any future user of bufioreq.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

---
Please note, this is a split/cleanup/hardening of Julien's PoC:
"Add support for Guest IO forwarding to a device emulator"

Changes V5 -> V6:
   - new patch
---
---
 xen/common/ioreq.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/common/ioreq.c b/xen/common/ioreq.c
index 67ef1f7..a36137d 100644
--- a/xen/common/ioreq.c
+++ b/xen/common/ioreq.c
@@ -629,6 +629,9 @@ static int ioreq_server_create(struct domain *d, int 
bufioreq_handling,
     unsigned int i;
     int rc;
 
+    if ( !IS_ENABLED(CONFIG_X86) && bufioreq_handling )
+        return -EINVAL;
+
     if ( bufioreq_handling > HVM_IOREQSRV_BUFIOREQ_ATOMIC )
         return -EINVAL;
 
-- 
2.7.4