Re: [RFC PATCH v7 05/16] arm64/mm: Add support for XPFO

[Konrad Rzeszutek Wilk]

On Thu, Jan 10, 2019 at 02:09:37PM -0700, Khalid Aziz wrote:
> From: Juerg Haefliger <juerg.haefliger@xxxxxxxxxxxxx>
> 
> Enable support for eXclusive Page Frame Ownership (XPFO) for arm64 and
> provide a hook for updating a single kernel page table entry (which is
> required by the generic XPFO code).
> 
> v6: use flush_tlb_kernel_range() instead of __flush_tlb_one()
> 
> CC: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Signed-off-by: Juerg Haefliger <juerg.haefliger@xxxxxxxxxxxxx>
> Signed-off-by: Tycho Andersen <tycho@xxxxxxxxxx>
> Signed-off-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
> ---
>  arch/arm64/Kconfig     |  1 +
>  arch/arm64/mm/Makefile |  2 ++
>  arch/arm64/mm/xpfo.c   | 58 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 61 insertions(+)
>  create mode 100644 arch/arm64/mm/xpfo.c
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index ea2ab0330e3a..f0a9c0007d23 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -171,6 +171,7 @@ config ARM64
>  	select SWIOTLB
>  	select SYSCTL_EXCEPTION_TRACE
>  	select THREAD_INFO_IN_TASK
> +	select ARCH_SUPPORTS_XPFO
>  	help
>  	  ARM 64-bit (AArch64) Linux support.
>  
> diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
> index 849c1df3d214..cca3808d9776 100644
> --- a/arch/arm64/mm/Makefile
> +++ b/arch/arm64/mm/Makefile
> @@ -12,3 +12,5 @@ KASAN_SANITIZE_physaddr.o	+= n
>  
>  obj-$(CONFIG_KASAN)		+= kasan_init.o
>  KASAN_SANITIZE_kasan_init.o	:= n
> +
> +obj-$(CONFIG_XPFO)		+= xpfo.o
> diff --git a/arch/arm64/mm/xpfo.c b/arch/arm64/mm/xpfo.c
> new file mode 100644
> index 000000000000..678e2be848eb
> --- /dev/null
> +++ b/arch/arm64/mm/xpfo.c
> @@ -0,0 +1,58 @@
> +/*
> + * Copyright (C) 2017 Hewlett Packard Enterprise Development, L.P.
> + * Copyright (C) 2016 Brown University. All rights reserved.
> + *
> + * Authors:
> + *   Juerg Haefliger <juerg.haefliger@xxxxxxx>
> + *   Vasileios P. Kemerlis <vpk@xxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + */
> +
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +
> +#include <asm/tlbflush.h>
> +
> +/*
> + * Lookup the page table entry for a virtual address and return a pointer to
> + * the entry. Based on x86 tree.
> + */
> +static pte_t *lookup_address(unsigned long addr)

The x86 also has level. Would it make sense to include that in here?