KVM: x86 emulator: add Src2 decode set

Instruction like shld has three operands, so we need to add a Src2
decode set. We start with Src2None, Src2CL, and Src2ImmByte, Src2One to
support shld/shrd and we will expand it later.

Signed-off-by: Guillaume Thouvenin <guillaume.thouvenin@ext.bull.net>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 30 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_x86_emulate.h b/arch/x86/include/asm/kvm_x86_emulate.h
index 16a002655f31..6a159732881a 100644
--- a/arch/x86/include/asm/kvm_x86_emulate.h
+++ b/arch/x86/include/asm/kvm_x86_emulate.h
@@ -123,6 +123,7 @@ struct decode_cache {
         u8 ad_bytes;
         u8 rex_prefix;
         struct operand src;
+        struct operand src2;
         struct operand dst;
         bool has_seg_override;
         u8 seg_override;
diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 7a07ca46c8ae..7f5cd62362c5 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -70,6 +70,12 @@
 #define Group       (1<<14)     /* Bits 3:5 of modrm byte extend opcode */
 #define GroupDual   (1<<15)     /* Alternate decoding of mod == 3 */
 #define GroupMask   0xff        /* Group number stored in bits 0:7 */
+/* Source 2 operand type */
+#define Src2None    (0<<29)
+#define Src2CL      (1<<29)
+#define Src2ImmByte (2<<29)
+#define Src2One     (3<<29)
+#define Src2Mask    (7<<29)
 
 enum {
         Group1_80, Group1_81, Group1_82, Group1_83,
@@ -1000,6 +1006,29 @@ done_prefixes:
                 break;
         }
 
+        /*
+         * Decode and fetch the second source operand: register, memory
+         * or immediate.
+         */
+        switch (c->d & Src2Mask) {
+        case Src2None:
+                break;
+        case Src2CL:
+                c->src2.bytes = 1;
+                c->src2.val = c->regs[VCPU_REGS_RCX] & 0x8;
+                break;
+        case Src2ImmByte:
+                c->src2.type = OP_IMM;
+                c->src2.ptr = (unsigned long *)c->eip;
+                c->src2.bytes = 1;
+                c->src2.val = insn_fetch(u8, 1, c->eip);
+                break;
+        case Src2One:
+                c->src2.bytes = 1;
+                c->src2.val = 1;
+                break;
+        }
+
         /* Decode and fetch the destination operand: register or memory. */
         switch (c->d & DstMask) {
         case ImplicitOps: