On Wed, 2020-05-13 at 17:04 +0200, Thomas Gleixner wrote:
>
>
> Balbir Singh <sbl...@amazon.com> writes:
> >
> > + if (prev_mm & LAST_USER_MM_L1D_FLUSH)
> > + arch_l1d_flush(0); /* Just flush, don't populate the
> > TLB */
>
> Bah. I fundamentally hate tail comments. They are just disturbing the
> reading flow. Aside of that, this states the WHAT but not the WHY. And
> if you add that explanation then you need more than 20 characters and
> end up with
>
> if (prev_mm & LAST_USER_MM_L1D_FLUSH) {
> /*
> * Proper comment explaining why this is flushing
> * without prepopulating the TLB.
> */
> arch_l1d_flush(0);
> }
>
I added a comment due to the use of 0, 0 is usually seen as true or
false and I wanted to add some comments in there to indicate we don't
populate the TLB, the reason we don't do it is, I don't think we need
to. I am happy to revisit the placement of the comment.
> anyway. And even for a short comment which fits after the function
> call
> it's way better to have:
>
> if (prev_mm & LAST_USER_MM_L1D_FLUSH) {
> /* Short explanation */
> arch_l1d_flush(0);
> }
>
> Hmm?
>
> > + /*
> > + * Leave last_user_mm_spec at LAST_USER_MM_IBPB, we don't
> > + * want to set LAST_USER_MM_L1D_FLUSH and force a flush before
> > + * we've allocated the flush pages.
>
> Ah here is the comment. I still like the explicit define for the (re)
> init.
>
I saw your tree and it sounds like you fixed it up in there in patch 3.
Balbir Singh.
