Re: [PATCH 7/8] KVM: x86 emulator: simplify instruction decode flags for opcodes E0-FF

[Gleb Natapov <gleb@redhat.com>]

On Mon, Aug 23, 2010 at 02:06:16PM +0300, Avi Kivity wrote:
> Use the new byte/word dual opcode decode.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  arch/x86/kvm/emulate.c |    6 ++----
>  1 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index c61f73d..6cb5663 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2464,13 +2464,11 @@ static struct opcode opcode_table[256] = {
>  	N, N, N, N, N, N, N, N,
>  	/* 0xE0 - 0xE7 */
>  	X3(D(SrcImmByte)), N,
> -	D(ByteOp | SrcImmUByte | DstAcc), D(SrcImmUByte | DstAcc),
> -	D(ByteOp | SrcAcc | DstImmUByte), D(SrcAcc | DstImmUByte),
> +	D2bv(SrcImmUByte | DstAcc), D2bv(SrcAcc | DstImmUByte),
>  	/* 0xE8 - 0xEF */
>  	D(SrcImm | Stack), D(SrcImm | ImplicitOps),
>  	D(SrcImmFAddr | No64), D(SrcImmByte | ImplicitOps),
> -	D(SrcNone | ByteOp | DstAcc), D(SrcNone | DstAcc),
> -	D(ByteOp | SrcAcc | ImplicitOps), D(SrcAcc | ImplicitOps),
> +	D2bv(SrcNone | DstAcc),	D2bv(SrcAcc | ImplicitOps),
>  	/* 0xF0 - 0xF7 */
>  	N, N, N, N,
>  	D(ImplicitOps | Priv), D(ImplicitOps), G(ByteOp, group3), G(0, group3),
Hmm. I actually have a patch that makes encoding of those to be different.

===
    Some instructions has 32 bit operand even in long mode.
    
    Decode this through decode table instead of during instruction
    emulation.

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 3b35e13..b4361fa 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -84,6 +84,7 @@
 #define Group       (1<<14)     /* Bits 3:5 of modrm byte extend opcode */
 #define GroupDual   (1<<15)     /* Alternate decoding of mod == 3 */
 /* Misc flags */
+#define Op32in64    (1<<22) /* Operand is 32b even in long mode */
 #define NoAccess    (1<<23) /* Don't access memory (lea/invlpg/verr etc) */
 #define Op3264      (1<<24) /* Operand is 64b in long mode, 32b otherwise */
 #define Undefined   (1<<25) /* No Such Instruction */
@@ -2472,13 +2473,13 @@ static struct opcode opcode_table[256] = {
 	N, N, N, N, N, N, N, N,
 	/* 0xE0 - 0xE7 */
 	X3(D(SrcImmByte)), N,
-	D(ByteOp | SrcImmUByte | DstAcc), D(SrcImmUByte | DstAcc),
-	D(ByteOp | SrcAcc | DstImmUByte), D(SrcAcc | DstImmUByte),
+	D(ByteOp | SrcImmUByte | DstAcc), D(SrcImmUByte | DstAcc | Op32in64),
+	D(ByteOp | SrcAcc | DstImmUByte), D(SrcAcc | DstImmUByte | Op32in64),
 	/* 0xE8 - 0xEF */
 	D(SrcImm | Stack), D(SrcImm | ImplicitOps),
 	D(SrcImmFAddr | No64), D(SrcImmByte | ImplicitOps),
-	D(SrcNone | ByteOp | DstAcc), D(SrcNone | DstAcc),
-	D(ByteOp | SrcAcc | ImplicitOps), D(SrcAcc | ImplicitOps),
+	D(SrcNone | ByteOp | DstAcc), D(SrcNone | DstAcc | Op32in64),
+	D(ByteOp | SrcAcc | ImplicitOps), D(SrcAcc | ImplicitOps | Op32in64),
 	/* 0xF0 - 0xF7 */
 	N, N, N, N,
 	D(ImplicitOps | Priv), D(ImplicitOps), G(ByteOp, group3), G(0, group3),
@@ -2750,6 +2751,9 @@ done_prefixes:
 			c->op_bytes = 4;
 	}
 
+	if (mode == X86EMUL_MODE_PROT64 && (c->d & Op32in64))
+		c->op_bytes = 4;
+
 	/* ModRM and SIB bytes. */
 	if (c->d & ModRM) {
 		rc = decode_modrm(ctxt, ops, &memop);
@@ -3295,7 +3299,6 @@ special_insn:
 	case 0xed: /* in (e/r)ax,dx */
 		c->src.val = c->regs[VCPU_REGS_RDX];
 	do_io_in:
-		c->dst.bytes = min(c->dst.bytes, 4u);
 		if (!emulator_io_permited(ctxt, ops, c->src.val, c->dst.bytes)) {
 			emulate_gp(ctxt, 0);
 			goto done;
@@ -3308,7 +3311,6 @@ special_insn:
 	case 0xef: /* out dx,(e/r)ax */
 		c->dst.val = c->regs[VCPU_REGS_RDX];
 	do_io_out:
-		c->src.bytes = min(c->src.bytes, 4u);
 		if (!emulator_io_permited(ctxt, ops, c->dst.val,
 					  c->src.bytes)) {
 			emulate_gp(ctxt, 0);
--
			Gleb.