argo: introduce the argo_op hypercall boilerplate

Presence is gated upon CONFIG_ARGO.

Registers the hypercall previously reserved for this.
Takes 5 arguments, does nothing and returns -ENOSYS.

Will be avoiding a compat ABI by using fixed-size types in hypercall ops so
HYPERCALL, rather than COMPAT_CALL, is the correct macro for the hypercall
tables.

Even though handles will be used for (up to) two of the arguments to the
hypercall, there will be no need for any XLAT_* translation functions
because the referenced data structures have been constructed to be exactly
the same size and bit pattern on both 32-bit and 64-bit guests, and padded
to be integer multiples of 32 bits in size. This means that the same
copy_to_guest and copy_from_guest logic can be relied upon to perform as
required without any further intervention. Testing communication with 32
and 64 bit guests has confirmed this works as intended.

Signed-off-by: Christopher Clark <[email protected]>
Acked-by: Jan Beulich <[email protected]>

v2 Copyright line: add 2019
v2 feedback xen-project#3 Jan: drop "message" from argo_message_op
v2 feedback xen-project#3 Jan: add Acked-by
v1 feedback #15 Jan: handle upper-halves of hypercall args
v1 feedback #15 Jan: use unsigned where negative values impossible

Author: dozylynx

xen/arch/x86/guest/hypercall_page.S

@@ -59,7 +59,7 @@ DECLARE_HYPERCALL(sysctl)
 DECLARE_HYPERCALL(domctl)
 DECLARE_HYPERCALL(kexec_op)
 DECLARE_HYPERCALL(tmem_op)
-DECLARE_HYPERCALL(xc_reserved_op)
+DECLARE_HYPERCALL(argo_op)
 DECLARE_HYPERCALL(xenpmu_op)
 
 DECLARE_HYPERCALL(arch_0)

xen/arch/x86/hvm/hypercall.c

@@ -133,6 +133,9 @@ static const hypercall_table_t hvm_hypercall_table[] = {
     HYPERCALL(domctl),
 #ifdef CONFIG_TMEM
     HYPERCALL(tmem_op),
+#endif
+#ifdef CONFIG_ARGO
+    HYPERCALL(argo_op),
 #endif
     COMPAT_CALL(platform_op),
 #ifdef CONFIG_PV

xen/arch/x86/hypercall.c

@@ -64,6 +64,9 @@ const hypercall_args_t hypercall_args_table[NR_hypercalls] =
     ARGS(domctl, 1),
     ARGS(kexec_op, 2),
     ARGS(tmem_op, 1),
+#ifdef CONFIG_ARGO
+    ARGS(argo_op, 5),
+#endif
     ARGS(xenpmu_op, 2),
 #ifdef CONFIG_HVM
     ARGS(hvm_op, 2),

xen/arch/x86/pv/hypercall.c

@@ -76,6 +76,9 @@ const hypercall_table_t pv_hypercall_table[] = {
 #endif
 #ifdef CONFIG_TMEM
     HYPERCALL(tmem_op),
+#endif
+#ifdef CONFIG_ARGO
+    HYPERCALL(argo_op),
 #endif
     HYPERCALL(xenpmu_op),
 #ifdef CONFIG_HVM

xen/common/Makefile

@@ -1,3 +1,4 @@
+obj-$(CONFIG_ARGO) += argo.o
 obj-y += bitmap.o
 obj-y += bsearch.o
 obj-$(CONFIG_CORE_PARKING) += core_parking.o

xen/common/argo.c

@@ -0,0 +1,28 @@
+/******************************************************************************
+ * Argo : Hypervisor-Mediated data eXchange
+ *
+ * Derived from v4v, the version 2 of v2v.
+ *
+ * Copyright (c) 2010, Citrix Systems
+ * Copyright (c) 2018-2019 BAE Systems
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <xen/errno.h>
+#include <xen/guest_access.h>
+
+long
+do_argo_op(unsigned int cmd, XEN_GUEST_HANDLE_PARAM(void) arg1,
+           XEN_GUEST_HANDLE_PARAM(void) arg2, unsigned long arg3,
+           unsigned long arg4)
+{
+    return -ENOSYS;
+}

xen/include/public/xen.h

@@ -118,7 +118,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
 #define __HYPERVISOR_domctl               36
 #define __HYPERVISOR_kexec_op             37
 #define __HYPERVISOR_tmem_op              38
-#define __HYPERVISOR_xc_reserved_op       39 /* reserved for XenClient */
+#define __HYPERVISOR_argo_op              39
 #define __HYPERVISOR_xenpmu_op            40
 #define __HYPERVISOR_dm_op                41
 

xen/include/xen/hypercall.h

@@ -136,6 +136,15 @@ do_tmem_op(
     XEN_GUEST_HANDLE_PARAM(tmem_op_t) uops);
 #endif
 
+#ifdef CONFIG_ARGO
+extern long do_argo_op(
+    unsigned int cmd,
+    XEN_GUEST_HANDLE_PARAM(void) arg1,
+    XEN_GUEST_HANDLE_PARAM(void) arg2,
+    unsigned long arg3,
+    unsigned long arg4);
+#endif
+
 extern long
 do_xenoprof_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg);