x86/fpu/mpx: Rework MPX 'xstate' types

MPX includes two separate "extended state components".  There is
no real need to have an 'mpx_struct' because we never really
manage the states together.

We also separate out the actual data in 'mpx_bndcsr_state' from
the padding.  We will shortly be checking the state sizes
against our structures and need them to match.  For consistency,
we also ensure to prefix these types with 'mpx_'.

Lastly, we add some comments to mirror some of the descriptions
in the Intel documents (SDM) of the various state components.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: dave@sr71.net
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20150902233129.384B73EB@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 23 insertions, 6 deletions

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 9f579305dd11..4d8c2009b94e 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -141,20 +141,37 @@ struct ymmh_struct {
 };
 
 /* Intel MPX support: */
-struct bndreg {
+
+struct mpx_bndreg {
 	u64				lower_bound;
 	u64				upper_bound;
 } __packed;
+/*
+ * State component 3 is used for the 4 128-bit bounds registers
+ */
+struct mpx_bndreg_state {
+	struct mpx_bndreg		bndreg[4];
+} __packed;
 
-struct bndcsr {
+/*
+ * State component 4 is used for the 64-bit user-mode MPX
+ * configuration register BNDCFGU and the 64-bit MPX status
+ * register BNDSTATUS.  We call the pair "BNDCSR".
+ */
+struct mpx_bndcsr {
 	u64				bndcfgu;
 	u64				bndstatus;
 } __packed;
 
-struct mpx_struct {
-	struct bndreg			bndreg[4];
-	struct bndcsr			bndcsr;
-};
+/*
+ * The BNDCSR state is padded out to be 64-bytes in size.
+ */
+struct mpx_bndcsr_state {
+	union {
+		struct mpx_bndcsr		bndcsr;
+		u8				pad_to_64_bytes[64];
+	};
+} __packed;
 
 struct xstate_header {
 	u64				xfeatures;