Re: [PATCHv5 4/4] KVM: emulator: optimize "rep ins" handling.

[Avi Kivity <avi@redhat.com>]

On 07/30/2012 05:38 PM, Gleb Natapov wrote:
> Optimize "rep ins" by allowing emulator to write back more than one
> datum at a time. Introduce new operand type OP_MEM_STR which tells
> writeback() that dst contains pointer to an array that should be written
> back as opposite to just one data element.
> 
>  	}
>  
> -	memcpy(dest, rc->data + rc->pos, size);
> -	rc->pos += size;
> +	if (ctxt->rep_prefix && !(ctxt->eflags & EFLG_DF)) {
> +		ctxt->dst.data = rc->data + rc->pos;
> +		ctxt->dst.type = OP_MEM_STR;
> +		ctxt->dst.count = (rc->end - rc->pos) / size;
> +		rc->pos = rc->end;

Should take into account the segment limit.

> +	} else {
> +		memcpy(dest, rc->data + rc->pos, size);
> +		rc->pos += size;
> +	}
>  	return 1;
>  }
>  
> @@ -1500,6 +1507,14 @@ static int writeback(struct x86_emulate_ctxt *ctxt)
>  		if (rc != X86EMUL_CONTINUE)
>  			return rc;
>  		break;
> +	case OP_MEM_STR:
> +		rc = segmented_write(ctxt,
> +				ctxt->dst.addr.mem,
> +				ctxt->dst.data,
> +				ctxt->dst.bytes * ctxt->dst.count);
> +		if (rc != X86EMUL_CONTINUE)
> +			return rc;
> +		break;
>  	case OP_XMM:
>  		write_sse_reg(ctxt, &ctxt->dst.vec_val, ctxt->dst.addr.xmm);
>  		break;
> @@ -2732,7 +2747,7 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
>  static void string_addr_inc(struct x86_emulate_ctxt *ctxt, int reg,
>  		struct operand *op)
>  {
> -	int df = (ctxt->eflags & EFLG_DF) ? -1 : 1;
> +	int df = (ctxt->eflags & EFLG_DF) ? -op->count : op->count;
>  
>  	register_address_increment(ctxt, &ctxt->regs[reg], df * op->bytes);
>  	op->addr.mem.ea = register_address(ctxt, ctxt->regs[reg]);
> @@ -3672,7 +3687,7 @@ static struct opcode opcode_table[256] = {
>  	I(DstReg | SrcMem | ModRM | Src2Imm, em_imul_3op),
>  	I(SrcImmByte | Mov | Stack, em_push),
>  	I(DstReg | SrcMem | ModRM | Src2ImmByte, em_imul_3op),
> -	I2bvIP(DstDI | SrcDX | Mov | String, em_in, ins, check_perm_in), /* insb, insw/insd */
> +	I2bvIP(DstDI | SrcDX | Mov | String | Unaligned, em_in, ins, check_perm_in), /* insb, insw/insd */

Eww.

>  	I2bvIP(SrcSI | DstDX | String, em_out, outs, check_perm_out), /* outsb, outsw/outsd */
>  	/* 0x70 - 0x7F */
>  	X16(D(SrcImmByte)),
> @@ -3930,6 +3945,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
>  			register_address(ctxt, ctxt->regs[VCPU_REGS_RDI]);
>  		op->addr.mem.seg = VCPU_SREG_ES;
>  		op->val = 0;
> +		op->count = 1;
>  		break;
>  	case OpDX:
>  		op->type = OP_REG;
> @@ -3973,6 +3989,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
>  			register_address(ctxt, ctxt->regs[VCPU_REGS_RSI]);
>  		op->addr.mem.seg = seg_override(ctxt);
>  		op->val = 0;
> +		op->count = 1;
>  		break;
>  	case OpImmFAddr:
>  		op->type = OP_IMM;
> @@ -4513,8 +4530,14 @@ writeback:
>  		string_addr_inc(ctxt, VCPU_REGS_RDI, &ctxt->dst);
>  
>  	if (ctxt->rep_prefix && (ctxt->d & String)) {
> +		unsigned int count;
>  		struct read_cache *r = &ctxt->io_read;
> -		register_address_increment(ctxt, &ctxt->regs[VCPU_REGS_RCX], -1);
> +		if ((ctxt->d & SrcMask) == SrcSI)
> +			count = ctxt->src.count;
> +		else
> +			count = ctxt->dst.count;

Does this work correctly for 'rep movs' and friends?


-- 
error compiling committee.c: too many arguments to function