Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote: > > From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > > The entry/exit text and cpu_entry_area are mapped into userspace and > the kernel. But, they are not _PAGE_GLOBAL. This creates unnecessary > TLB misses. > > Add the _PAGE_GLOBAL flag for these areas. > > static void __init > diff -puN arch/x86/mm/pti.c~kpti-why-no-global arch/x86/mm/pti.c > --- a/arch/x86/mm/pti.c~kpti-why-no-global 2018-03-21 16:32:00.799192311 -0700 > +++ b/arch/x86/mm/pti.c 2018-03-21 16:32:00.803192311 -0700 > @@ -300,6 +300,13 @@ pti_clone_pmds(unsigned long start, unsi > return; > > /* > + * Setting 'target_pmd' below creates a mapping in both > + * the user and kernel page tables. It is effectively > + * global, so set it as global in both copies. > + */ > + *pmd = pmd_set_flags(*pmd, _PAGE_GLOBAL); if (boot_cpu_has(X86_FEATURE_PGE)) ?
