arm: xen: implement multicall hypercall support.

As part of this make the usual change to xen_ulong_t in place of unsigned long.
This change has no impact on x86.

The Linux definition of struct multicall_entry.result differs from the Xen
definition, I think for good reasons, and used a long rather than an unsigned
long. Therefore introduce a xen_long_t, which is a long on x86 architectures
and a signed 64-bit integer on ARM.

Use uint32_t nr_calls on x86 for consistency with the ARM definition.

Build tested on amd64 and i386 builds. Runtime tested on ARM.

Signed-off-by: Ian Campbell <[e-mail]>
Cc: Stefano Stabellini <[e-mail]>
Cc: Konrad Rzeszutek Wilk <[e-mail]>
Cc: Boris Ostrovsky <[e-mail]>
Signed-off-by: David Vrabel <[e-mail]>

arch/arm/include/asm/xen/hypercall.h

···
 int HYPERVISOR_physdev_op(int cmd, void *arg);
 int HYPERVISOR_vcpu_op(int cmd, int vcpuid, void *extra_args);
 int HYPERVISOR_tmem_op(void *arg);
+int HYPERVISOR_multicall(struct multicall_entry *calls, uint32_t nr);
 
 static inline void
 MULTI_update_va_mapping(struct multicall_entry *mcl, unsigned long va,
···
 	BUG();
 }
 
-static inline int
-HYPERVISOR_multicall(void *call_list, int nr_calls)
-{
-	BUG();
-}
 #endif /* _ASM_ARM_XEN_HYPERCALL_H */

arch/arm/include/asm/xen/interface.h

···
 #define PRI_xen_pfn "llx"
 typedef uint64_t xen_ulong_t;
 #define PRI_xen_ulong "llx"
+typedef int64_t xen_long_t;
+#define PRI_xen_long "llx"
 /* Guest handles for primitive C types. */
 __DEFINE_GUEST_HANDLE(uchar, unsigned char);
 __DEFINE_GUEST_HANDLE(uint,  unsigned int);

arch/arm/xen/hypercall.S

···
 HYPERCALL2(physdev_op);
 HYPERCALL3(vcpu_op);
 HYPERCALL1(tmem_op);
+HYPERCALL2(multicall);
 
 ENTRY(privcmd_call)
 	stmdb sp!, {r4}

arch/arm64/xen/hypercall.S

···
 HYPERCALL2(physdev_op);
 HYPERCALL3(vcpu_op);
 HYPERCALL1(tmem_op);
+HYPERCALL2(multicall);
 
 ENTRY(privcmd_call)
 	mov x16, x0

arch/x86/include/asm/xen/hypercall.h

···
 }
 
 static inline int
-HYPERVISOR_multicall(void *call_list, int nr_calls)
+HYPERVISOR_multicall(void *call_list, uint32_t nr_calls)
 {
 	return _hypercall2(int, multicall, call_list, nr_calls);
 }

arch/x86/include/asm/xen/interface.h

···
 #define PRI_xen_pfn "lx"
 typedef unsigned long xen_ulong_t;
 #define PRI_xen_ulong "lx"
+typedef long xen_long_t;
+#define PRI_xen_long "lx"
+
 /* Guest handles for primitive C types. */
 __DEFINE_GUEST_HANDLE(uchar, unsigned char);
 __DEFINE_GUEST_HANDLE(uint,  unsigned int);

include/xen/interface/xen.h

···
  * NB. The fields are natural register size for this architecture.
  */
 struct multicall_entry {
-    unsigned long op;
-    long result;
-    unsigned long args[6];
+    xen_ulong_t op;
+    xen_long_t result;
+    xen_ulong_t args[6];
 };
 DEFINE_GUEST_HANDLE_STRUCT(multicall_entry);