Re: [PATCH 23/43] x86/mm/kaiser: Introduce user-mapped per-cpu areas

[Borislav Petkov]

On Fri, Nov 24, 2017 at 06:23:51PM +0100, Ingo Molnar wrote:
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> 
> These patches are based on work from a team at Graz University of
> Technology posted here: https://github.com/IAIK/KAISER
> 
> The KAISER approach keeps two copies of the page tables: one for running
> in the kernel and one for running userspace.  But, there are a few
> structures that are needed for switching in and out of the kernel and
> a good subset of *those* are per-cpu data.
> 
> This patch creates a new kind of per-cpu data that is mapped and

Never say "This patch" in the commit message of a patch. It is
tautologically useless.

> can be used no matter which copy of the page tables is active.
> Users of this new section will be forthcoming.
> 
> Thanks to Hugh Dickins for cleanups to this code.
> 
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: daniel.gruss@xxxxxxxxxxxxxx
> Cc: hughd@xxxxxxxxxx
> Cc: keescook@xxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Cc: luto@xxxxxxxxxx
> Cc: michael.schwarz@xxxxxxxxxxxxxx
> Cc: moritz.lipp@xxxxxxxxxxxxxx
> Cc: richard.fellner@xxxxxxxxxxxxxxxxx
> Link: https://lkml.kernel.org/r/20171123003444.196CB6DB@xxxxxxxxxxxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
>  include/asm-generic/vmlinux.lds.h |  7 +++++++
>  include/linux/percpu-defs.h       | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index bdcd1caae092..e12168936d3f 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -826,7 +826,14 @@
>   */
>  #define PERCPU_INPUT(cacheline)						\
>  	VMLINUX_SYMBOL(__per_cpu_start) = .;				\
> +	VMLINUX_SYMBOL(__per_cpu_user_mapped_start) = .;		\
>  	*(.data..percpu..first)						\
> +	. = ALIGN(cacheline);						\
> +	*(.data..percpu..user_mapped)					\
> +	*(.data..percpu..user_mapped..shared_aligned)			\
> +	. = ALIGN(PAGE_SIZE);						\
> +	*(.data..percpu..user_mapped..page_aligned)			\
> +	VMLINUX_SYMBOL(__per_cpu_user_mapped_end) = .;			\
>  	. = ALIGN(PAGE_SIZE);						\
>  	*(.data..percpu..page_aligned)					\
>  	. = ALIGN(cacheline);						\
> diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
> index 2d2096ba1cfe..752513674295 100644
> --- a/include/linux/percpu-defs.h
> +++ b/include/linux/percpu-defs.h
> @@ -35,6 +35,12 @@
>  
>  #endif
>  
> +#ifdef CONFIG_KAISER
> +#define USER_MAPPED_SECTION "..user_mapped"
> +#else
> +#define USER_MAPPED_SECTION ""
> +#endif
>  /*
>   * Base implementations of per-CPU variable declarations and definitions, where
>   * the section in which the variable is to be placed is provided by the
> @@ -115,6 +121,12 @@
>  #define DEFINE_PER_CPU(type, name)					\
>  	DEFINE_PER_CPU_SECTION(type, name, "")
>  
> +#define DECLARE_PER_CPU_USER_MAPPED(type, name)				\
> +	DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
> +
> +#define DEFINE_PER_CPU_USER_MAPPED(type, name)				\
> +	DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
> +
>  /*
>   * Declaration/definition used for per-CPU variables that must come first in
>   * the set of variables.
> @@ -144,6 +156,14 @@
>  	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
>  	____cacheline_aligned_in_smp
>  
> +#define DECLARE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name)		\
> +	DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
> +	____cacheline_aligned_in_smp
> +
> +#define DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name)		\
> +	DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
> +	____cacheline_aligned_in_smp
> +
>  #define DECLARE_PER_CPU_ALIGNED(type, name)				\
>  	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)	\
>  	____cacheline_aligned
> @@ -162,6 +182,16 @@
>  #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name)				\
>  	DEFINE_PER_CPU_SECTION(type, name, "..page_aligned")		\
>  	__aligned(PAGE_SIZE)
> +/*
> + * Declaration/definition used for per-CPU variables that must be page aligned and need to be mapped in user mode.
> + */

WARNING: line over 100 characters
#122: FILE: include/linux/percpu-defs.h:186:
+ * Declaration/definition used for per-CPU variables that must be page aligned and need to be mapped in user mode.

> +#define DECLARE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name)		\
> +	DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
> +	__aligned(PAGE_SIZE)
> +
> +#define DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name)		\
> +	DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
> +	__aligned(PAGE_SIZE)
>  
>  /*
>   * Declaration/definition used for per-CPU variables that must be read mostly.
> -- 

With that:

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

-- 
Regards/Gruss,
    Boris.

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