Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote: > On 02/16/2018 09:47 AM, Nadav Amit wrote: >>> But, this also means that we now get *no* opportunity to use >>> global pages with PTI, even for data which is shared such as the >>> cpu_entry_area and entry/exit text. >> >> Doesn’t this patch change the kernel behavior when the “nopti” >> parameter is used? > > I don't think so. It takes the "nopti" behavior and effectively makes > it apply everywhere. So it changes the PTI behavior, not the "nopti" > behavior. > > Maybe it would help to quote the code that you think does this instead > of the description. :) Sorry, I thought it is obvious - so I must be missing something. > +#ifdef CONFIG_PAGE_TABLE_ISOLATION > +#define __PAGE_KERNEL_GLOBAL 0 > +#else > +#define __PAGE_KERNEL_GLOBAL _PAGE_GLOBAL > +#endif ... > --- a/arch/x86/mm/pageattr.c~kpti-no-global-for-kernel-mappings 2018-02-13 15:17:56.148210060 -0800 > +++ b/arch/x86/mm/pageattr.c 2018-02-13 15:17:56.153210060 -0800 > @@ -593,7 +593,8 @@ try_preserve_large_page(pte_t *kpte, uns > * different bit positions in the two formats. > */ > req_prot = pgprot_4k_2_large(req_prot); > - req_prot = pgprot_set_on_present(req_prot, _PAGE_GLOBAL | _PAGE_PSE); > + req_prot = pgprot_set_on_present(req_prot, > + __PAGE_KERNEL_GLOBAL | _PAGE_PSE); > req_prot = canon_pgprot(req_prot); >From these chunks, it seems to me as req_prot will not have the global bit on when “nopti” parameter is provided. What am I missing? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href
