KVM: x86 emulator: Decode memory operands directly into a 'struct operand'

Since modrm operand can be either register or memory, decoding it into
a 'struct operand', which can represent both, is simpler.

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

2 files changed, 57 insertions, 71 deletions

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index e425444658e8..1e4a72ce301a 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -203,9 +203,6 @@ struct decode_cache {
         u8 modrm_rm;
         u8 modrm_seg;
         bool rip_relative;
-        unsigned long modrm_ea;
-        void *modrm_ptr;
-        unsigned long modrm_val;
         struct fetch_cache fetch;
         struct read_cache io_read;
         struct read_cache mem_read;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index eda69411d050..955d48074648 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -581,12 +581,14 @@ static void decode_register_operand(struct operand *op,
 }
 
 static int decode_modrm(struct x86_emulate_ctxt *ctxt,
-                        struct x86_emulate_ops *ops)
+                        struct x86_emulate_ops *ops,
+                        struct operand *op)
 {
         struct decode_cache *c = &ctxt->decode;
         u8 sib;
         int index_reg = 0, base_reg = 0, scale;
         int rc = X86EMUL_CONTINUE;
+        ulong modrm_ea = 0;
 
         if (c->rex_prefix) {
                 c->modrm_reg = (c->rex_prefix & 4) << 1;        /* REX.R */
@@ -598,16 +600,19 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
         c->modrm_mod |= (c->modrm & 0xc0) >> 6;
         c->modrm_reg |= (c->modrm & 0x38) >> 3;
         c->modrm_rm |= (c->modrm & 0x07);
-        c->modrm_ea = 0;
         c->modrm_seg = VCPU_SREG_DS;
 
         if (c->modrm_mod == 3) {
-                c->modrm_ptr = decode_register(c->modrm_rm,
+                op->type = OP_REG;
+                op->bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
+                op->addr.reg = decode_register(c->modrm_rm,
                                                c->regs, c->d & ByteOp);
-                c->modrm_val = *(unsigned long *)c->modrm_ptr;
+                fetch_register_operand(op);
                 return rc;
         }
 
+        op->type = OP_MEM;
+
         if (c->ad_bytes == 2) {
                 unsigned bx = c->regs[VCPU_REGS_RBX];
                 unsigned bp = c->regs[VCPU_REGS_RBP];
@@ -618,46 +623,46 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
                 switch (c->modrm_mod) {
                 case 0:
                         if (c->modrm_rm == 6)
-                                c->modrm_ea += insn_fetch(u16, 2, c->eip);
+                                modrm_ea += insn_fetch(u16, 2, c->eip);
                         break;
                 case 1:
-                        c->modrm_ea += insn_fetch(s8, 1, c->eip);
+                        modrm_ea += insn_fetch(s8, 1, c->eip);
                         break;
                 case 2:
-                        c->modrm_ea += insn_fetch(u16, 2, c->eip);
+                        modrm_ea += insn_fetch(u16, 2, c->eip);
                         break;
                 }
                 switch (c->modrm_rm) {
                 case 0:
-                        c->modrm_ea += bx + si;
+                        modrm_ea += bx + si;
                         break;
                 case 1:
-                        c->modrm_ea += bx + di;
+                        modrm_ea += bx + di;
                         break;
                 case 2:
-                        c->modrm_ea += bp + si;
+                        modrm_ea += bp + si;
                         break;
                 case 3:
-                        c->modrm_ea += bp + di;
+                        modrm_ea += bp + di;
                         break;
                 case 4:
-                        c->modrm_ea += si;
+                        modrm_ea += si;
                         break;
                 case 5:
-                        c->modrm_ea += di;
+                        modrm_ea += di;
                         break;
                 case 6:
                         if (c->modrm_mod != 0)
-                                c->modrm_ea += bp;
+                                modrm_ea += bp;
                         break;
                 case 7:
-                        c->modrm_ea += bx;
+                        modrm_ea += bx;
                         break;
                 }
                 if (c->modrm_rm == 2 || c->modrm_rm == 3 ||
                     (c->modrm_rm == 6 && c->modrm_mod != 0))
                         c->modrm_seg = VCPU_SREG_SS;
-                c->modrm_ea = (u16)c->modrm_ea;
+                modrm_ea = (u16)modrm_ea;
         } else {
                 /* 32/64-bit ModR/M decode. */
                 if ((c->modrm_rm & 7) == 4) {
@@ -667,48 +672,51 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
                         scale = sib >> 6;
 
                         if ((base_reg & 7) == 5 && c->modrm_mod == 0)
-                                c->modrm_ea += insn_fetch(s32, 4, c->eip);
+                                modrm_ea += insn_fetch(s32, 4, c->eip);
                         else
-                                c->modrm_ea += c->regs[base_reg];
+                                modrm_ea += c->regs[base_reg];
                         if (index_reg != 4)
-                                c->modrm_ea += c->regs[index_reg] << scale;
+                                modrm_ea += c->regs[index_reg] << scale;
                 } else if ((c->modrm_rm & 7) == 5 && c->modrm_mod == 0) {
                         if (ctxt->mode == X86EMUL_MODE_PROT64)
                                 c->rip_relative = 1;
                 } else
-                        c->modrm_ea += c->regs[c->modrm_rm];
+                        modrm_ea += c->regs[c->modrm_rm];
                 switch (c->modrm_mod) {
                 case 0:
                         if (c->modrm_rm == 5)
-                                c->modrm_ea += insn_fetch(s32, 4, c->eip);
+                                modrm_ea += insn_fetch(s32, 4, c->eip);
                         break;
                 case 1:
-                        c->modrm_ea += insn_fetch(s8, 1, c->eip);
+                        modrm_ea += insn_fetch(s8, 1, c->eip);
                         break;
                 case 2:
-                        c->modrm_ea += insn_fetch(s32, 4, c->eip);
+                        modrm_ea += insn_fetch(s32, 4, c->eip);
                         break;
                 }
         }
+        op->addr.mem = modrm_ea;
 done:
         return rc;
 }
 
 static int decode_abs(struct x86_emulate_ctxt *ctxt,
-                      struct x86_emulate_ops *ops)
+                      struct x86_emulate_ops *ops,
+                      struct operand *op)
 {
         struct decode_cache *c = &ctxt->decode;
         int rc = X86EMUL_CONTINUE;
 
+        op->type = OP_MEM;
         switch (c->ad_bytes) {
         case 2:
-                c->modrm_ea = insn_fetch(u16, 2, c->eip);
+                op->addr.mem = insn_fetch(u16, 2, c->eip);
                 break;
         case 4:
-                c->modrm_ea = insn_fetch(u32, 4, c->eip);
+                op->addr.mem = insn_fetch(u32, 4, c->eip);
                 break;
         case 8:
-                c->modrm_ea = insn_fetch(u64, 8, c->eip);
+                op->addr.mem = insn_fetch(u64, 8, c->eip);
                 break;
         }
 done:
@@ -2280,6 +2288,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt)
         int mode = ctxt->mode;
         int def_op_bytes, def_ad_bytes, dual, goffset;
         struct opcode opcode, *g_mod012, *g_mod3;
+        struct operand memop = { .type = OP_NONE };
 
         /* we cannot decode insn before we complete previous rep insn */
         WARN_ON(ctxt->restart);
@@ -2418,25 +2427,25 @@ done_prefixes:
 
         /* ModRM and SIB bytes. */
         if (c->d & ModRM) {
-                rc = decode_modrm(ctxt, ops);
+                rc = decode_modrm(ctxt, ops, &memop);
                 if (!c->has_seg_override)
                         set_seg_override(c, c->modrm_seg);
         } else if (c->d & MemAbs)
-                rc = decode_abs(ctxt, ops);
+                rc = decode_abs(ctxt, ops, &memop);
         if (rc != X86EMUL_CONTINUE)
                 goto done;
 
         if (!c->has_seg_override)
                 set_seg_override(c, VCPU_SREG_DS);
 
-        if (!(!c->twobyte && c->b == 0x8d))
-                c->modrm_ea += seg_override_base(ctxt, ops, c);
+        if (memop.type == OP_MEM && !(!c->twobyte && c->b == 0x8d))
+                memop.addr.mem += seg_override_base(ctxt, ops, c);
 
-        if (c->ad_bytes != 8)
-                c->modrm_ea = (u32)c->modrm_ea;
+        if (memop.type == OP_MEM && c->ad_bytes != 8)
+                memop.addr.mem = (u32)memop.addr.mem;
 
-        if (c->rip_relative)
-                c->modrm_ea += c->eip;
+        if (memop.type == OP_MEM && c->rip_relative)
+                memop.addr.mem += c->eip;
 
         /*
          * Decode and fetch the source operand: register, memory
@@ -2449,31 +2458,16 @@ done_prefixes:
                 decode_register_operand(&c->src, c, 0);
                 break;
         case SrcMem16:
-                c->src.bytes = 2;
+                memop.bytes = 2;
                 goto srcmem_common;
         case SrcMem32:
-                c->src.bytes = 4;
+                memop.bytes = 4;
                 goto srcmem_common;
         case SrcMem:
-                c->src.bytes = (c->d & ByteOp) ? 1 :
+                memop.bytes = (c->d & ByteOp) ? 1 :
                                                            c->op_bytes;
-                /* Don't fetch the address for invlpg: it could be unmapped. */
-                if (c->d & NoAccess)
-                        break;
         srcmem_common:
-                /*
-                 * For instructions with a ModR/M byte, switch to register
-                 * access if Mod = 3.
-                 */
-                if ((c->d & ModRM) && c->modrm_mod == 3) {
-                        c->src.type = OP_REG;
-                        c->src.val = c->modrm_val;
-                        c->src.addr.reg = c->modrm_ptr;
-                        break;
-                }
-                c->src.type = OP_MEM;
-                c->src.addr.mem = c->modrm_ea;
-                c->src.val = 0;
+                c->src = memop;
                 break;
         case SrcImm:
         case SrcImmU:
@@ -2543,9 +2537,8 @@ done_prefixes:
                 insn_fetch_arr(c->src.valptr, c->src.bytes, c->eip);
                 break;
         case SrcMemFAddr:
-                c->src.type = OP_MEM;
-                c->src.addr.mem = c->modrm_ea;
-                c->src.bytes = c->op_bytes + 2;
+                memop.bytes = c->op_bytes + 2;
+                goto srcmem_common;
                 break;
         }
 
@@ -2583,26 +2576,18 @@ done_prefixes:
                 break;
         case DstMem:
         case DstMem64:
-                if ((c->d & ModRM) && c->modrm_mod == 3) {
-                        c->dst.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
-                        c->dst.type = OP_REG;
-                        c->dst.val = c->dst.orig_val = c->modrm_val;
-                        c->dst.addr.reg = c->modrm_ptr;
-                        break;
-                }
-                c->dst.type = OP_MEM;
-                c->dst.addr.mem = c->modrm_ea;
+                c->dst = memop;
                 if ((c->d & DstMask) == DstMem64)
                         c->dst.bytes = 8;
                 else
                         c->dst.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
-                c->dst.val = 0;
-                if (c->d & BitOp) {
+                if (c->dst.type == OP_MEM && (c->d & BitOp)) {
                         unsigned long mask = ~(c->dst.bytes * 8 - 1);
 
                         c->dst.addr.mem = c->dst.addr.mem +
                                                    (c->src.val & mask) / 8;
                 }
+                c->dst.orig_val = c->dst.val;
                 break;
         case DstAcc:
                 c->dst.type = OP_REG;
@@ -2682,11 +2667,15 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
         }
 
         if (c->src.type == OP_MEM) {
+                if (c->d & NoAccess)
+                        goto no_fetch;
                 rc = read_emulated(ctxt, ops, c->src.addr.mem,
                                         c->src.valptr, c->src.bytes);
                 if (rc != X86EMUL_CONTINUE)
                         goto done;
                 c->src.orig_val64 = c->src.val64;
+        no_fetch:
+                ;
         }
 
         if (c->src2.type == OP_MEM) {