Re: [PATCH v15 06/26] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW

Dave Hansen
2020-12-03T15:12:58Z

On 12/3/20 1:19 AM, Borislav Petkov wrote:
> On Tue, Nov 10, 2020 at 08:21:51AM -0800, Yu-cheng Yu wrote:
>> Before introducing _PAGE_COW for non-hardware memory management purposes in
>> the next patch, rename _PAGE_DIRTY to _PAGE_DIRTY_HW and _PAGE_BIT_DIRTY to
>> _PAGE_BIT_DIRTY_HW to make meanings more clear. There are no functional
>> changes from this patch.
> There's no guarantee for "next" or "this" patch when a patch gets
> applied so reword your commit message pls.
>
> Also, I fail to understand here what _PAGE_DIRTY_HW makes more clear?
> The page dirty bit is clear enough to me so why the churn?

Once upon a time in this set, we had:

_PAGE_DIRTY (the old hardware bit)
and
_PAGE_DIRTY_SW (the new shadow stack necessitated bit)

In *that* case, it made sense to change the name of the hardware one to
help differentiate them. But, over time, we changed _PAGE_DIRTY_SW to
_PAGE_COW.

I think you're right. The renaming is just churn now with the current
naming.