Re: [PATCH 03/23] x86, kaiser: disable global pages

[Thomas Gleixner]

On Tue, 31 Oct 2017, Dave Hansen wrote:
> --- a/arch/x86/include/asm/pgtable_types.h~kaiser-prep-disable-global-pages	2017-10-31 15:03:49.314064402 -0700
> +++ b/arch/x86/include/asm/pgtable_types.h	2017-10-31 15:03:49.323064827 -0700
> @@ -47,7 +47,12 @@
>  #define _PAGE_ACCESSED	(_AT(pteval_t, 1) << _PAGE_BIT_ACCESSED)
>  #define _PAGE_DIRTY	(_AT(pteval_t, 1) << _PAGE_BIT_DIRTY)
>  #define _PAGE_PSE	(_AT(pteval_t, 1) << _PAGE_BIT_PSE)
> +#ifdef CONFIG_X86_GLOBAL_PAGES
>  #define _PAGE_GLOBAL	(_AT(pteval_t, 1) << _PAGE_BIT_GLOBAL)
> +#else
> +/* We must ensure that kernel TLBs are unusable while in userspace */
> +#define _PAGE_GLOBAL	(_AT(pteval_t, 0))
> +#endif

What you really want to do here is to clear PAGE_GLOBAL in the
supported_pte_mask. probe_page_size_mask() is the proper place for that.

This allows both .config and boottime configuration.

Thanks,

	tglx