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SubjectRe: [RFC PATCH v7 05/16] arm64/mm: Add support for XPFO
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On 1/23/19 7:20 AM, Konrad Rzeszutek Wilk wrote:
> On Thu, Jan 10, 2019 at 02:09:37PM -0700, Khalid Aziz wrote:
>> From: Juerg Haefliger <juerg.haefliger@canonical.com>
>>
>> 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@lists.infradead.org
>> Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
>> Signed-off-by: Tycho Andersen <tycho@docker.com>
>> Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
>> ---
>> 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@hpe.com>
>> + * Vasileios P. Kemerlis <vpk@cs.brown.edu>
>> + *
>> + * 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?
>

Possibly. ARM64 does not define page levels (as in the enum for page
levels) at this time but that can be added easily. Adding level to
lookup_address() for arm will make it uniform with x86 but is there any
other rationale besides that? Do you see a future use for this
information? The only other architecture I could see that defines
lookup_address() is sh but it uses it for trapped io only.

Thanks,
Khalid
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