[PATCH 03/24] x86/mm/kaiser: Introduce user-mapped per-CPU areas

[Ingo Molnar]

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
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: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: daniel.gruss@xxxxxxxxxxxxxx
Cc: hughd@xxxxxxxxxx
Cc: keescook@xxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
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.
+ */
+#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.
-- 
2.14.1