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SubjectRe: [patch 33/60] x86/mm/kpti: Allocate a separate user PGD
On Mon, Dec 04, 2017 at 03:07:39PM +0100, Thomas Gleixner wrote:
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> Kernel page table isolation requires to have two PGDs. One for the kernel,
> which contains the full kernel mapping plus the user space mapping and one
> for user space which contains the user space mappings and the minimal set
> of kernel mappings which are required by the architecture to be able to
> transition from and to user space.
>
> Add the necessary preliminaries.
>
> [ tglx: Split out from the big kaiser dump ]
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>
> ---
> arch/x86/kernel/head_64.S | 30 +++++++++++++++++++++++++++---
> arch/x86/mm/pgtable.c | 16 ++++++++++++++--
> 2 files changed, 41 insertions(+), 5 deletions(-)

...

> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -355,14 +355,26 @@ static inline void _pgd_free(pgd_t *pgd)
> kmem_cache_free(pgd_cache, pgd);
> }
> #else
> +
> +#ifdef CONFIG_KERNEL_PAGE_TABLE_ISOLATION
> +/*
> + * Instead of one pgd, we aquire two pgds. Being order-1, it is

"acquire"

Otherwise:

Reviewed-by: Borislav Petkov <bp@suse.de>

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

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