Re: [PATCH 1/3] KVM: emulator: check rex prefix inside decode_register()

[Gleb Natapov <gleb@redhat.com>]

On Mon, Nov 04, 2013 at 03:04:54PM +0100, Paolo Bonzini wrote:
> Il 04/11/2013 14:52, Gleb Natapov ha scritto:
> > All decode_register() callers check if instruction has rex prefix
> > to properly decode one byte operand. It make sense to move the check
> > inside.
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> 
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> 
> I guess you'd like to use Linus's extra week and get it in 3.13?
> 
Yes, nothing serious here.

> Paolo
> 
> > ---
> >  arch/x86/kvm/emulate.c | 18 +++++++-----------
> >  1 file changed, 7 insertions(+), 11 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> > index 282d28c..0bd372f 100644
> > --- a/arch/x86/kvm/emulate.c
> > +++ b/arch/x86/kvm/emulate.c
> > @@ -785,9 +785,10 @@ static int do_insn_fetch(struct x86_emulate_ctxt *ctxt,
> >   * @highbyte_regs specifies whether to decode AH,CH,DH,BH.
> >   */
> >  static void *decode_register(struct x86_emulate_ctxt *ctxt, u8 modrm_reg,
> > -			     int highbyte_regs)
> > +			     int byteop)
> >  {
> >  	void *p;
> > +	int highbyte_regs = (ctxt->rex_prefix == 0) && byteop;
> >  
> >  	if (highbyte_regs && modrm_reg >= 4 && modrm_reg < 8)
> >  		p = (unsigned char *)reg_rmw(ctxt, modrm_reg & 3) + 1;
> > @@ -1024,7 +1025,6 @@ static void decode_register_operand(struct x86_emulate_ctxt *ctxt,
> >  				    struct operand *op)
> >  {
> >  	unsigned reg = ctxt->modrm_reg;
> > -	int highbyte_regs = ctxt->rex_prefix == 0;
> >  
> >  	if (!(ctxt->d & ModRM))
> >  		reg = (ctxt->b & 7) | ((ctxt->rex_prefix & 1) << 3);
> > @@ -1046,10 +1046,10 @@ static void decode_register_operand(struct x86_emulate_ctxt *ctxt,
> >  
> >  	op->type = OP_REG;
> >  	if (ctxt->d & ByteOp) {
> > -		op->addr.reg = decode_register(ctxt, reg, highbyte_regs);
> > +		op->addr.reg = decode_register(ctxt, reg, true);
> >  		op->bytes = 1;
> >  	} else {
> > -		op->addr.reg = decode_register(ctxt, reg, 0);
> > +		op->addr.reg = decode_register(ctxt, reg, false);
> >  		op->bytes = ctxt->op_bytes;
> >  	}
> >  	fetch_register_operand(op);
> > @@ -1082,12 +1082,10 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
> >  	ctxt->modrm_seg = VCPU_SREG_DS;
> >  
> >  	if (ctxt->modrm_mod == 3) {
> > -		int highbyte_regs = ctxt->rex_prefix == 0;
> > -
> >  		op->type = OP_REG;
> >  		op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;
> >  		op->addr.reg = decode_register(ctxt, ctxt->modrm_rm,
> > -					       highbyte_regs && (ctxt->d & ByteOp));
> > +				ctxt->d & ByteOp);
> >  		if (ctxt->d & Sse) {
> >  			op->type = OP_XMM;
> >  			op->bytes = 16;
> > @@ -4117,10 +4115,8 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
> >  	case OpMem8:
> >  		ctxt->memop.bytes = 1;
> >  		if (ctxt->memop.type == OP_REG) {
> > -			int highbyte_regs = ctxt->rex_prefix == 0;
> > -
> > -			ctxt->memop.addr.reg = decode_register(ctxt, ctxt->modrm_rm,
> > -					       highbyte_regs);
> > +			ctxt->memop.addr.reg = decode_register(ctxt,
> > +					ctxt->modrm_rm, true);
> >  			fetch_register_operand(&ctxt->memop);
> >  		}
> >  		goto mem_common;
> > 

--
			Gleb.