On 03.07.20 17:36, Catalin Marinas wrote:
> From: Steven Price <steven.price@xxxxxxx>
>
> For arm64 MTE support it is necessary to be able to mark pages that
> contain user space visible tags that will need to be saved/restored e.g.
> when swapped out.
>
> To support this add a new arch specific flag (PG_arch_2). This flag is
> only available on 64-bit architectures due to the limited number of
> spare page flags on the 32-bit ones.
>
> Signed-off-by: Steven Price <steven.price@xxxxxxx>
> [catalin.marinas@xxxxxxx: use CONFIG_64BIT for guarding this new flag]
> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
> Notes:
> v6:
> - Using CONFIG_64BIT instead of a new CONFIG_ARCH_USES_PG_ARCH_2 option.
>
> New in v4.
>
> fs/proc/page.c | 3 +++
> include/linux/kernel-page-flags.h | 1 +
> include/linux/page-flags.h | 3 +++
> include/trace/events/mmflags.h | 9 ++++++++-
> tools/vm/page-types.c | 2 ++
> 5 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index f909243d4a66..9f1077d94cde 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -217,6 +217,9 @@ u64 stable_page_flags(struct page *page)
> u |= kpf_copy_bit(k, KPF_PRIVATE_2, PG_private_2);
> u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1);
> u |= kpf_copy_bit(k, KPF_ARCH, PG_arch_1);
> +#ifdef CONFIG_64BIT
> + u |= kpf_copy_bit(k, KPF_ARCH_2, PG_arch_2);
> +#endif
>
> return u;
> };
> diff --git a/include/linux/kernel-page-flags.h b/include/linux/kernel-page-flags.h
> index abd20ef93c98..eee1877a354e 100644
> --- a/include/linux/kernel-page-flags.h
> +++ b/include/linux/kernel-page-flags.h
> @@ -17,5 +17,6 @@
> #define KPF_ARCH 38
> #define KPF_UNCACHED 39
> #define KPF_SOFTDIRTY 40
> +#define KPF_ARCH_2 41
>
> #endif /* LINUX_KERNEL_PAGE_FLAGS_H */
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 6be1aa559b1e..276140c94f4a 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -135,6 +135,9 @@ enum pageflags {
> #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
> PG_young,
> PG_idle,
> +#endif
> +#ifdef CONFIG_64BIT
> + PG_arch_2,
> #endif
> __NR_PAGEFLAGS,
People are usually *very* picky when it comes to new page flags. It
somewhat concerns me that we bump up __NR_PAGEFLAGS for any 64bit arch.
That feels wrong.
--
Thanks,
David / dhildenb
