2017-06-01 07:36:24

by Paolo Bonzini

Subject: Re: [PATCH v5] KVM: x86: avoid large stack allocations in em_fxrstor

On 01/06/2017 03:05, Nick Desaulniers wrote:
> On Wed, May 31, 2017 at 07:01:29AM -0400, Paolo Bonzini wrote:
>>> + size = offsetof(struct fxregs_state, xmm_space[16]);
>> This still has the same issue (it should be multiplied by 4).
>
> I'm still misunderstanding the math here.
>
> Why multiplied by four, in this case? 8 * 16 / 4 is used in other cases.

*16/4 is the same as *4. :)

Paolo

2017-06-02 02:10:22

by Nick Desaulniers

Subject: Re: [PATCH v5] KVM: x86: avoid large stack allocations in em_fxrstor

On Thu, Jun 01, 2017 at 09:36:18AM +0200, Paolo Bonzini wrote:
> On 01/06/2017 03:05, Nick Desaulniers wrote:
> > On Wed, May 31, 2017 at 07:01:29AM -0400, Paolo Bonzini wrote:
> >>> + size = offsetof(struct fxregs_state, xmm_space[16]);
> >> This still has the same issue (it should be multiplied by 4).
> >
> > I'm still misunderstanding the math here.
> >
> > Why multiplied by four, in this case? 8 * 16 / 4 is used in other cases.
>
> *16/4 is the same as *4. :)

I meant the use of an expression full of literals rather than either a
single literal or an expression formed from well named variables seemed
kind of like a code smell, but w/e. Patch inbound.