[PATCH v3 08/13] xen/x86: don't use hypercall table for calling compat hypercalls

[Juergen Gross <jgross@xxxxxxxx>]

Today the *_op_compat hypercalls call the modern handler functions by
using the entries from the hypercall table. This is resulting in a
not needed indirect function call which can be avoided by using the
correct handler function directly. This is basically a revert of
commit 1252e282311734 ("86/pv: Export pv_hypercall_table[] rather
than working around it in several ways"), which reasoning no longer
applies, as shim no longer modifies the hypercall table.

The hypercall table can now be made static as there is no external
reference to it any longer.

Commit 834cb8761051f7 ("x86/PV32: fix physdev_op_compat handling")
can be reverted, too, as using the direct call of the correct handler
is already handled fine without that patch.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/compat.c           | 14 ++++----------
 xen/arch/x86/pv/hypercall.c     |  9 ++++++++-
 xen/arch/x86/x86_64/compat.c    |  1 -
 xen/include/asm-x86/hypercall.h |  8 --------
 4 files changed, 12 insertions(+), 20 deletions(-)

diff --git a/xen/arch/x86/compat.c b/xen/arch/x86/compat.c
index 58b202f701..939b449dec 100644
--- a/xen/arch/x86/compat.c
+++ b/xen/arch/x86/compat.c
@@ -17,14 +17,12 @@ typedef long ret_t;
 /* Legacy hypercall (as of 0x00030202). */
 ret_t do_physdev_op_compat(XEN_GUEST_HANDLE_PARAM(physdev_op_t) uop)
 {
-    typeof(do_physdev_op) *fn =
-        (void *)pv_hypercall_table[__HYPERVISOR_physdev_op].native;
     struct physdev_op op;
 
     if ( unlikely(copy_from_guest(&op, uop, 1) != 0) )
         return -EFAULT;
 
-    return fn(op.cmd, guest_handle_from_ptr(&uop.p->u, void));
+    return do_physdev_op(op.cmd, guest_handle_from_ptr(&uop.p->u, void));
 }
 
 #ifndef COMPAT
@@ -32,14 +30,11 @@ ret_t 
do_physdev_op_compat(XEN_GUEST_HANDLE_PARAM(physdev_op_t) uop)
 /* Legacy hypercall (as of 0x00030101). */
 long do_sched_op_compat(int cmd, unsigned long arg)
 {
-    typeof(do_sched_op) *fn =
-        (void *)pv_hypercall_table[__HYPERVISOR_sched_op].native;
-
     switch ( cmd )
     {
     case SCHEDOP_yield:
     case SCHEDOP_block:
-        return fn(cmd, guest_handle_from_ptr(NULL, void));
+        return do_sched_op(cmd, guest_handle_from_ptr(NULL, void));
 
     case SCHEDOP_shutdown:
         TRACE_3D(TRC_SCHED_SHUTDOWN,
@@ -57,8 +52,6 @@ long do_sched_op_compat(int cmd, unsigned long arg)
 /* Legacy hypercall (as of 0x00030202). */
 long do_event_channel_op_compat(XEN_GUEST_HANDLE_PARAM(evtchn_op_t) uop)
 {
-    typeof(do_event_channel_op) *fn =
-        (void *)pv_hypercall_table[__HYPERVISOR_event_channel_op].native;
     struct evtchn_op op;
 
     if ( unlikely(copy_from_guest(&op, uop, 1) != 0) )
@@ -76,7 +69,8 @@ long 
do_event_channel_op_compat(XEN_GUEST_HANDLE_PARAM(evtchn_op_t) uop)
     case EVTCHNOP_bind_ipi:
     case EVTCHNOP_bind_vcpu:
     case EVTCHNOP_unmask:
-        return fn(op.cmd, guest_handle_from_ptr(&uop.p->u, void));
+        return do_event_channel_op(op.cmd,
+                                   guest_handle_from_ptr(&uop.p->u, void));
 
     default:
         return -ENOSYS;
diff --git a/xen/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
index abe4dd7839..c391d18130 100644
--- a/xen/arch/x86/pv/hypercall.c
+++ b/xen/arch/x86/pv/hypercall.c
@@ -27,6 +27,13 @@
 #include <asm/multicall.h>
 #include <irq_vectors.h>
 
+typedef struct {
+    hypercall_fn_t *native;
+#ifdef CONFIG_PV32
+    hypercall_fn_t *compat;
+#endif
+} pv_hypercall_table_t;
+
 #ifdef CONFIG_PV32
 #define HYPERCALL(x)                                                \
     [ __HYPERVISOR_ ## x ] = { (hypercall_fn_t *) do_ ## x,         \
@@ -40,7 +47,7 @@
 #define COMPAT_CALL(x) HYPERCALL(x)
 #endif
 
-const pv_hypercall_table_t pv_hypercall_table[] = {
+static const pv_hypercall_table_t pv_hypercall_table[] = {
     COMPAT_CALL(set_trap_table),
     HYPERCALL(mmu_update),
     COMPAT_CALL(set_gdt),
diff --git a/xen/arch/x86/x86_64/compat.c b/xen/arch/x86/x86_64/compat.c
index fcbc1cc0d7..0e4c71f2aa 100644
--- a/xen/arch/x86/x86_64/compat.c
+++ b/xen/arch/x86/x86_64/compat.c
@@ -12,7 +12,6 @@ EMIT_FILE;
 #define physdev_op_t                  physdev_op_compat_t
 #define do_physdev_op                 compat_physdev_op
 #define do_physdev_op_compat(x)       compat_physdev_op_compat(_##x)
-#define native                        compat
 
 #define COMPAT
 #define _XEN_GUEST_HANDLE(t) XEN_GUEST_HANDLE(t)
diff --git a/xen/include/asm-x86/hypercall.h b/xen/include/asm-x86/hypercall.h
index 2547572ccd..eb2907b5b6 100644
--- a/xen/include/asm-x86/hypercall.h
+++ b/xen/include/asm-x86/hypercall.h
@@ -21,13 +21,6 @@ typedef unsigned long hypercall_fn_t(
     unsigned long, unsigned long, unsigned long,
     unsigned long, unsigned long);
 
-typedef struct {
-    hypercall_fn_t *native;
-#ifdef CONFIG_PV32
-    hypercall_fn_t *compat;
-#endif
-} pv_hypercall_table_t;
-
 typedef struct {
     uint8_t native;
 #ifdef CONFIG_COMPAT
@@ -38,7 +31,6 @@ typedef struct {
 extern const hypercall_args_t hypercall_args_table[NR_hypercalls];
 
 #ifdef CONFIG_PV
-extern const pv_hypercall_table_t pv_hypercall_table[];
 void pv_hypercall(struct cpu_user_regs *regs);
 #endif
 
-- 
2.26.2