x86: add linux kernel support for YMM state

Impact: save/restore Intel-AVX state properly between tasks

Intel Advanced Vector Extensions (AVX) introduce 256-bit vector processing
capability. More about AVX at http://software.intel.com/sites/avx

Add OS support for YMM state management using xsave/xrstor infrastructure
to support AVX.
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1239402084.27006.8057.camel@localhost.localdomain>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/include/asm/processor.h

@@ -352,6 +352,11 @@ struct i387_soft_struct {
 	u32			entry_eip;
 };
 
+struct ymmh_struct {
+	/* 16 * 16 bytes for each YMMH-reg = 256 bytes */
+	u32 ymmh_space[64];
+};
+
 struct xsave_hdr_struct {
 	u64 xstate_bv;
 	u64 reserved1[2];
@@ -361,6 +366,7 @@ struct xsave_hdr_struct {
 struct xsave_struct {
 	struct i387_fxsave_struct i387;
 	struct xsave_hdr_struct xsave_hdr;
+	struct ymmh_struct ymmh;
 	/* new processor state extensions will go here */
 } __attribute__ ((packed, aligned (64)));
 

arch/x86/include/asm/sigcontext.h

@@ -269,6 +269,11 @@ struct _xsave_hdr {
 	__u64 reserved2[5];
 };
 
+struct _ymmh_state {
+	/* 16 * 16 bytes for each YMMH-reg */
+	__u32 ymmh_space[64];
+};
+
 /*
  * Extended state pointed by the fpstate pointer in the sigcontext.
  * In addition to the fpstate, information encoded in the xstate_hdr
@@ -278,6 +283,7 @@ struct _xsave_hdr {
 struct _xstate {
 	struct _fpstate fpstate;
 	struct _xsave_hdr xstate_hdr;
+	struct _ymmh_state ymmh;
 	/* new processor state extensions go here */
 };
 

arch/x86/include/asm/xsave.h

@@ -7,6 +7,7 @@
 
 #define XSTATE_FP	0x1
 #define XSTATE_SSE	0x2
+#define XSTATE_YMM	0x4
 
 #define XSTATE_FPSSE	(XSTATE_FP | XSTATE_SSE)
 
@@ -15,7 +16,7 @@
 /*
  * These are the features that the OS can handle currently.
  */
-#define XCNTXT_MASK	(XSTATE_FP | XSTATE_SSE)
+#define XCNTXT_MASK	(XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
 
 #ifdef CONFIG_X86_64
 #define REX_PREFIX	"0x48, "

arch/x86/kernel/xsave.c

@@ -324,7 +324,7 @@ void __ref xsave_cntxt_init(void)
 	}
 
 	/*
-	 * for now OS knows only about FP/SSE
+	 * Support only the state known to OS.
 	 */
 	pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
 	xsave_init();