[PATCH 03/12] x86, pkey: pkru xsave fields and data structure

[Dave Hansen <dave@sr71.net>]

The protection keys register (PKRU) is saved and restored using
xsave.  Define the data structure that we will use to access it
inside the xsave buffer, and also double-check that the new
structure matches the size that comes out of the CPU.

---

 b/arch/x86/include/asm/processor.h |    9 +++++++++
 b/arch/x86/include/asm/xsave.h     |    3 ++-
 b/arch/x86/kernel/xsave.c          |    7 +++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff -puN arch/x86/include/asm/processor.h~pkeys-2-xsave arch/x86/include/asm/processor.h
--- a/arch/x86/include/asm/processor.h~pkeys-2-xsave	2015-05-07 10:31:41.756204056 -0700
+++ b/arch/x86/include/asm/processor.h	2015-05-07 10:31:41.763204372 -0700
@@ -406,6 +406,15 @@ struct bndcsr {
 	u64 bndstatus;
 } __packed;
 
+/*
+ * "The size of XSAVE state component for PKRU is 8 bytes,
+ *  of which only the first four bytes are used...".
+ */
+struct pkru {
+	u32 pkru;
+	u32 pkru_unused;
+} __packed;
+
 struct xsave_hdr_struct {
 	u64 xstate_bv;
 	u64 xcomp_bv;
diff -puN arch/x86/include/asm/xsave.h~pkeys-2-xsave arch/x86/include/asm/xsave.h
--- a/arch/x86/include/asm/xsave.h~pkeys-2-xsave	2015-05-07 10:31:41.758204147 -0700
+++ b/arch/x86/include/asm/xsave.h	2015-05-07 10:31:41.764204417 -0700
@@ -14,6 +14,7 @@
 #define XSTATE_OPMASK		0x20
 #define XSTATE_ZMM_Hi256	0x40
 #define XSTATE_Hi16_ZMM		0x80
+#define XSTATE_PKRU		0x200
 
 #define XSTATE_FPSSE	(XSTATE_FP | XSTATE_SSE)
 #define XSTATE_AVX512	(XSTATE_OPMASK | XSTATE_ZMM_Hi256 | XSTATE_Hi16_ZMM)
@@ -33,7 +34,7 @@
 			| XSTATE_OPMASK | XSTATE_ZMM_Hi256 | XSTATE_Hi16_ZMM)
 
 /* Supported features which require eager state saving */
-#define XSTATE_EAGER	(XSTATE_BNDREGS | XSTATE_BNDCSR)
+#define XSTATE_EAGER	(XSTATE_BNDREGS | XSTATE_BNDCSR | XSTATE_PKRU)
 
 /* All currently supported features */
 #define XCNTXT_MASK	(XSTATE_LAZY | XSTATE_EAGER)
diff -puN arch/x86/kernel/xsave.c~pkeys-2-xsave arch/x86/kernel/xsave.c
--- a/arch/x86/kernel/xsave.c~pkeys-2-xsave	2015-05-07 10:31:41.760204237 -0700
+++ b/arch/x86/kernel/xsave.c	2015-05-07 10:31:41.764204417 -0700
@@ -528,6 +528,13 @@ void setup_xstate_comp(void)
 					+ xstate_comp_sizes[i-1];
 
 	}
+	/*
+	 * Check that the size of the "PKRU" xsave area
+	 * which the CPU knows about matches the kernel
+	 * data structure that we have defined.
+	 */
+	if ((xstate_features >= XSTATE_PKRU) && xstate_comp_sizes[XSTATE_PKRU])
+		WARN_ON(xstate_comp_sizes[XSTATE_PKRU] != sizeof(struct pkru));
 }
 
 /*
_