On 01/02/16 17:08, Ard Biesheuvel wrote: > On 1 February 2016 at 17:20, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: >> On 01/02/16 15:36, Catalin Marinas wrote: >>> On Mon, Feb 01, 2016 at 01:34:16PM +0000, Marc Zyngier wrote: >>>> On 01/02/16 13:16, Christoffer Dall wrote: >>>>> On Mon, Jan 25, 2016 at 03:53:40PM +0000, Marc Zyngier wrote: >>>>>> diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S >>>>>> index 93e8d983..9e0683f 100644 >>>>>> --- a/arch/arm64/kvm/hyp/hyp-entry.S >>>>>> +++ b/arch/arm64/kvm/hyp/hyp-entry.S >>>>>> @@ -38,6 +38,32 @@ >>>>>> ldp x0, x1, [sp], #16 >>>>>> .endm >>>>>> >>>>>> +.macro do_el2_call >>>>>> + /* >>>>>> + * Shuffle the parameters before calling the function >>>>>> + * pointed to in x0. Assumes parameters in x[1,2,3]. >>>>>> + */ >>>>>> + stp lr, xzr, [sp, #-16]! >>>>> >>>>> remind me why this pair isn't just doing "str" instead of "stp" with the >>>>> xzr ? >>>> >>>> Because SP has to be aligned on a 16 bytes boundary at all times. >>> >>> You could do something like: >>> >>> sub sp, sp, #16 >>> str lr, [sp] >>> >> >> Ah, fair enough. I'll fold that in. >> > > Since we're micro-reviewing: what's wrong with > > str lr, [sp, #-16]! > > ? > I suspect that on most micro-architectures, a register writeback is going to be slower than doing the sub independently. I may be wrong, though. M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
