Re: [PATCH] x86 emulator: Add 'push/pop sreg' instructions

[Avi Kivity <avi@redhat.com>]

On 08/19/2009 07:11 AM, Mohammed Gamal wrote:
>
> +static void emulate_push_sreg(struct x86_emulate_ctxt *ctxt, int seg)
> +{
> +	struct decode_cache *c =&ctxt->decode;
> +	struct kvm_segment segment;
> +	
> +	if (ctxt->mode == X86EMUL_MODE_PROT64&&  (seg != VCPU_SREG_FS ||
> +						   seg != VCPU_SREG_GS)) {
> +		kvm_queue_exception(ctxt->vcpu, UD_VECTOR);
> +		return;
> +	}
>    

It's better to check at the callsite, in case the opcode is ever reused 
for a new instruction.  Or even better, add a new decode flag No64 so we 
can do this during the decode stage.

> +
> +static int emulate_pop_sreg(struct x86_emulate_ctxt *ctxt,
> +			     struct x86_emulate_ops *ops, int seg)
> +{
> +	struct decode_cache *c =&ctxt->decode;
> +	struct kvm_segment segment;
> +	int rc;
> +
> +	if (ctxt->mode == X86EMUL_MODE_PROT64&&  (seg != VCPU_SREG_FS ||
> +						    seg != VCPU_SREG_GS)) {
> +		kvm_queue_exception(ctxt->vcpu, UD_VECTOR);
> +		return -1;
> +	}
> +
> +	kvm_x86_ops->get_segment(ctxt->vcpu,&segment, seg);
> +	rc = emulate_pop(ctxt, ops,&segment.selector, c->op_bytes);
> +	if (rc != 0)
> +		return rc;
> +	
> +	rc = kvm_load_segment_descriptor(ctxt->vcpu, segment.selector, 1, seg);
> +	return rc;
> +}
>    

Why do the ->get_segment() at all?  pop into a temporary variable, and 
call kvm_load_segment_descriptor() with that.


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