Add standard extended feature bit 6 from the Intel SDM rev. 57, which

indicates that data-pointer in the saved x87 FPU state is only updated
on FPU exceptions.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

sys/x86/include/specialreg.h

@@ -335,6 +335,7 @@
 #define	CPUID_STDEXT_BMI1	0x00000008
 #define	CPUID_STDEXT_HLE	0x00000010
 #define	CPUID_STDEXT_AVX2	0x00000020
+#define	CPUID_STDEXT_FDP_EXC	0x00000040
 #define	CPUID_STDEXT_SMEP	0x00000080
 #define	CPUID_STDEXT_BMI2	0x00000100
 #define	CPUID_STDEXT_ERMS	0x00000200

sys/x86/x86/identcpu.c

@@ -932,6 +932,8 @@ printcpuinfo(void)
 				       "\005HLE"
 				       /* Advanced Vector Instructions 2 */
 				       "\006AVX2"
+				       /* FDP_EXCPTN_ONLY */
+				       "\007FDPEXC"
 				       /* Supervisor Mode Execution Prot. */
 				       "\010SMEP"
 				       /* Bit Manipulation Instructions */