KVM: x86 emulator: allow specifying group directly in opcode

Instead of having a group number, store the group table pointer directly in
the opcode.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 38 insertions, 9 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5e496127a01c..f3b984427d10 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -110,10 +110,21 @@ enum {
 
 struct opcode {
         u32 flags;
+        union {
+                struct opcode *group;
+                struct group_dual *gdual;
+        } u;
+};
+
+struct group_dual {
+        struct opcode mod012[8];
+        struct opcode mod3[8];
 };
 
 #define D(_y) { .flags = (_y) }
 #define N    D(0)
+#define G(_f, _g) { .flags = ((_f) | Group), .u.group = (_g) }
+#define GD(_f, _g) { .flags = ((_f) | Group | GroupDual), .u.gdual = (_g) }
 
 static struct opcode group_table[] = {
         [Group1*8] =
@@ -331,6 +342,8 @@ static struct opcode twobyte_table[256] = {
 
 #undef D
 #undef N
+#undef G
+#undef GD
 
 /* EFLAGS bit definitions. */
 #define EFLG_ID (1<<21)
@@ -930,8 +943,8 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
         struct decode_cache *c = &ctxt->decode;
         int rc = X86EMUL_CONTINUE;
         int mode = ctxt->mode;
-        int def_op_bytes, def_ad_bytes, group, dual;
-
+        int def_op_bytes, def_ad_bytes, group, dual, goffset;
+        struct opcode opcode, *g_mod012, *g_mod3;
 
         /* we cannot decode insn before we complete previous rep insn */
         WARN_ON(ctxt->restart);
@@ -1018,15 +1031,16 @@ done_prefixes:
                         c->op_bytes = 8;        /* REX.W */
 
         /* Opcode byte(s). */
-        c->d = opcode_table[c->b].flags;
-        if (c->d == 0) {
+        opcode = opcode_table[c->b];
+        if (opcode.flags == 0) {
                 /* Two-byte opcode? */
                 if (c->b == 0x0f) {
                         c->twobyte = 1;
                         c->b = insn_fetch(u8, 1, c->eip);
-                        c->d = twobyte_table[c->b].flags;
+                        opcode = twobyte_table[c->b];
                 }
         }
+        c->d = opcode.flags;
 
         if (c->d & Group) {
                 group = c->d & GroupMask;
@@ -1034,12 +1048,27 @@ done_prefixes:
                 c->modrm = insn_fetch(u8, 1, c->eip);
                 --c->eip;
 
-                group = (group << 3) + ((c->modrm >> 3) & 7);
+                if (group) {
+                        g_mod012 = g_mod3 = &group_table[group * 8];
+                        if (c->d & GroupDual)
+                                g_mod3 = &group2_table[group * 8];
+                } else {
+                        if (c->d & GroupDual) {
+                                g_mod012 = opcode.u.gdual->mod012;
+                                g_mod3 = opcode.u.gdual->mod3;
+                        } else
+                                g_mod012 = g_mod3 = opcode.u.group;
+                }
+
                 c->d &= ~(Group | GroupDual | GroupMask);
-                if (dual && (c->modrm >> 6) == 3)
-                        c->d |= group2_table[group].flags;
+
+                goffset = (c->modrm >> 3) & 7;
+
+                if ((c->modrm >> 6) == 3)
+                        opcode = g_mod3[goffset];
                 else
-                        c->d |= group_table[group].flags;
+                        opcode = g_mod012[goffset];
+                c->d |= opcode.flags;
         }
 
         /* Unrecognised? */