On Tue, Oct 28, 2014 at 10:22:28AM -0700, Andy Lutomirski wrote: > This adds CONFIG_X86_VSYSCALL_EMULATION, guarded by CONFIG_EXPERT. > Turning it off completely disables vsyscall emulation, saving ~3.5k > for vsyscall_64.c, 4k for vsyscall_emu_64.S (the fake vsyscall > page), some tiny amount of core mm code that supports a gate area, > and possibly 4k for a wasted pagetable. The latter is because the > vsyscall addresses are misaligned and fit poorly in the fixmap. > > Signed-off-by: Andy Lutomirski <[email protected]>
One minor nit below, but with or without that change, Reviewed-by: Josh Triplett <[email protected]> > --- a/arch/x86/xen/mmu.c > +++ b/arch/x86/xen/mmu.c > @@ -1456,11 +1456,13 @@ static int xen_pgd_alloc(struct mm_struct *mm) > user_pgd = (pgd_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO); > page->private = (unsigned long)user_pgd; > > +#ifdef CONFIG_X86_VSYSCALL_EMULATION > if (user_pgd != NULL) { > user_pgd[pgd_index(VSYSCALL_ADDR)] = > __pgd(__pa(level3_user_vsyscall) | _PAGE_TABLE); > ret = 0; > } > +#endif Could you instead make the if use IS_ENABLED? if (IS_ENABLED(CONFIG_X86_VSYSCALL_EMULATION) && user_pgd != NULL) That has the advantage of ensuring that the code continues to compile. (Given that you haven't removed level3_user_vsyscall, that should work.) - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
