Re: [PATCH V2] KVM/x86: Check input paging mode when cs.l is set

["Lan, Tianyu" <tianyu.lan@xxxxxxxxx>]

On 12/14/2017 7:41 PM, Paolo Bonzini wrote:
> On 14/12/2017 04:55, Lan Tianyu wrote:
> > +	 * When EFER.LME and CR0.PG are set, CR4.PAE and EFER.LMA
> > +	 * must be set.
> > +	 */
> > +	if ((sregs->efer & EFER_LME) && (sregs->cr0 & X86_CR0_PG_BIT)) {
> > +		if (!(sregs->cr4 & X86_CR4_PAE_BIT))
> > +			return -EINVAL;
> > +		if (!(sregs->efer & EFER_LMA))
> > +			return -EINVAL;
> > +	} else if (sregs->efer & EFER_LMA)
>
> This can just be "(sregs->efer & EFER_LMA) || sregs->cs.l", making the
> next "if" redundant.  Even better written as
>
> 	if ((sregs->efer & EFER_LME) && (sregs->cr0 & X86_CR0_PG_BIT)) {
> 		/*
> 		 * When EFER.LME and CR0.PG are set, the processor is in
> 		 * 64-bit mode (though maybe in a 32-bit code segment).
> 		 * CR4.PAE and EFER.LMA must be set.
> 		 */
> 		if (... || ...)
> 			return -EINVAL;
> 	} else {
> 		/*
> 		 * Not in 64-bit mode: EFER.LMA is clear and the code
> 		 * segment cannot be 64-bit.
> 		 */
> 		if (... || ...)
> 			return -EINVAL;
> 	}
>
> Paolo

OK. Thanks for your guide. just send v3. Please have a look.