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SubjectRe: [PATCH] x86/mm/pti: remove dead logic during user pagetable population
On Sun, 7 Jan 2018, Jike Song wrote:
> On Sun, Jan 7, 2018 at 3:33 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Sun, 7 Jan 2018, Jike Song wrote:
> >
> > Care to explain why you think this is not needed?
> >
>
> Hi Thomas,
>
> Look at one of the original code snippets:
>
> 162 if (pgd_none(*pgd)) {
> 163 unsigned long new_p4d_page = __get_free_page(gfp);
> 164 if (!new_p4d_page)
> 165 return NULL;
> 166
> 167 if (pgd_none(*pgd)) {
> 168 set_pgd(pgd, __pgd(_KERNPG_TABLE |
> __pa(new_p4d_page)));
> 169 new_p4d_page = 0;
> 170 }
> 171 if (new_p4d_page)
> 172 free_page(new_p4d_page);
> 173 }
>
> Correct me if I'm too dumb to see the rationale here, but to me there
> can't be any difference between
> two pgd_none(*pgd) of L162 and L167, so it is always false in L171.

Right, but this kind of explanation wants to be in the changelog. Empty
changelogs for this kind of change are just not acceptable.

Thanks,

tglx

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