Messages in this thread | | | Date | Tue, 14 Nov 2017 21:29:41 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCHv2 1/2] x86/mm: Do not allow non-MAP_FIXED mapping across DEFAULT_MAP_WINDOW border |
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On Tue, 14 Nov 2017, Kirill A. Shutemov wrote: > On Tue, Nov 14, 2017 at 05:01:50PM +0100, Thomas Gleixner wrote: > > +bool mmap_address_hint_valid(unsigned long addr, unsigned long len) > > +{ > > + if (TASK_SIZE - len < addr) > > + return false; > > +#if CONFIG_PGTABLE_LEVELS >= 5 > > + return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW); > > Is it micro optimization? I don't feel it necessary. It's not that hot > codepath to care about few cycles. (And one more place to care about for > boot-time switching.) > > If you think it's needed, maybe IS_ENABLED() instead?
You're right. It's can be unconditional, For page table levels < 5 its just redundant as its covered by the TASK_SIZE check already.
Thanks,
tglx
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