Re: [PATCH -v2] kvm: Emulate MOVBE

[Paolo Bonzini <pbonzini@redhat.com>]

Il 21/04/2013 14:23, Borislav Petkov ha scritto:
> On Sun, Apr 21, 2013 at 01:46:50PM +0200, Borislav Petkov wrote:
>> We probably need something with copying values to a temp variable or so.
> 
> Basically something like that:
> 
>         case 2:
>                 /*
>                  * From MOVBE definition: "...When the operand size is 16 bits,
>                  * the upper word of the destination register remains unchanged
>                  * ..."
>                  *
>                  * Both casting ->valptr and ->val to u16 breaks strict aliasing
>                  * rules so we have to do the operation almost per hand.
>                  */
>                 tmp = (u16)ctxt->src.val;
>                 ctxt->dst.val &= ~0xffffUL;
>                 ctxt->dst.val |= (unsigned long)swab16(tmp);
> 		break;
> 
> This passes all gcc checks, even the stricter ones when building with W=3.

I thought the valptr one was ok.  I find this one more readable, too.
How does the generated code look like?

Paolo